[Reprinted  from  the  Journal  of  The  American  Chemical  Society, 
Vol.  XXX.  Vol.  II.  November,  1908.I 


[Contribution  from  the  John  Harrison  Laboratory  of  Chemistry.] 

OBSERVATIONS  ON  COLUMBIUM. 

By  Clarence  W.  Balke  and  Edgar  F.  Smith. 

Received  August  23,  1908. 

Introduction. 

The  present  communication  contains  the  results  obtained  in  a con- 
tinuation of  the  investigation  of  the  compounds  of  columbium  and  tan- 
talum which  is  being  conducted  in  this  laboratory.  It  deals  with  the 
preparation  of  columbium  oxide  free  from  titanium  and  other  impuri- 
ties, the  preparation  of  columbium  chloride,  a determination  of  the  atomic 
weight  of  columbium  through  analyses  of  the  chloride,  and  a study  of 
a number  of  the  columbates  and  the  double  fluorides  of  columbium. 
It  also  includes  a study  of  certain  new  compounds  of  tantalum. 

Purification  of  the  Material. 

The  starting-out  material  used  in  the  present  investigation  consisted 
of  the  double  fluorides  of  potassium  and  columbium  which  had  been  ob- 
tained from  the  columbite  of  South  Dakota  by  Roy  D.  Hall  and  Edgar 
E.  Smith. ^ These  contained  as  impurities  traces  of  titanium,  tin,  tungsten, 
tantalum,  silicon  and  iron.  Of  these  impurities  previous  investigators 
have  found  titanium  the  most  difficult  to  remove.  After  a careful  in- 
vestigation of  the  hydrogen  peroxide  test  which  has  been  used  in  this 
laboratory  to  detect  traces  of  titanium  in  columbium  oxide,  and  having 
failed  to  obtain  an  oxide  which  did  not  give  a color  reaction  with  hy- 
drogen peroxide.  Hall  and  Smith  reached  the  following  conclusion;  “From 
these  experiments  it  may  be  safely  concluded  that  the  color  produced 
in  hydrofluoric  acid  solutions  of  columbium  with  hydrogen  peroxide 
is  not  due  to  the  presence  of  titanium.  Also,  it  is  likely  that  columbium 
^ This  Journae,  27,  1369  (1905). 


1638 


CI.ARENCK  W.  BALKE  AND  EDGAR  E.  SMITH. 


itself  gives  a distinctive  color  with  hydrogen  peroxide,  equivalent  to 
from  o.io  per  cent,  to  0.15  per  cent,  of  its  weight  of  titanium  dioxide, 
yet  yellow-green  instead  of  straw-yellow,  as  is  given  by  titanium  in  di- 
lute'solutions.  Possibly  there  may  still  be  present  some  other  element. 
For  this,  careful  search  will  be  made.” 

Moreover,  these  investigators  pointed  out  that  the  crystallization'  of 
potassium  columbium  fluoride  (K2CbF^), ' which  is  not  isomorphous 
with  potassium  titanium  fluoride,  might  serve  for  the  preparation  of 
columbium  compounds  free  from  titanium.  With  these  thoughts  in 
mind  it  was  determined  to  carry  out  this  crystallization  on  a large  scale. 

Potassium  columbium  fluoride,  K2CbF7,  is  produced  when  the  other 
double  fluorides  of  columbium  are  recrystallized  from  strong  hydro- 
fluoric acid.  Eighteen  kilograms  of  the  double  fluorides  of  potassium 
and  columbium  were  crystallized  four  times  from  aqueous  hydrofluoric 
acid  containing  approximately  20  per  cent,  of  the  pure  acid.  The  first 
crop  of  crystals  from  each  crystallization  served  as  the  starting-out  material 
for  the  next  crystallization.  The  mother  liquors  from  the  more  advanced 
crystallizations  were  used  to  further  crystallize  the  more  impure  material. 
For  the  first  two  crystallizations  commercial  acid  was  used,  but  for  the 
last  two  carefully  purified  acid  was  employed.  The  latter  was 
obtained  by  distilling  the  commercial  acid  from  a large  lead  jug  pro- 
vided with  a platinum  condenser.  Previous  to  the  distillation,  potassium 
hydroxide  was  added  to  the  acid  in  sufficient  quantities  to  combine 
with  all  of  the  hydrofluosilicic  acid  present.  The  potassium  fluosilicate 
formed  was  filtered  out,  large  rubber  funnels  being  employed.'  About 
one  hundred  kilograms  of  commercial  acid  were  required  to  complete 
the  crystallizations,  and  all  of  the  solutions,  when  not  perfectly  clear, 
were  filtered  through  large  rubber  funnels  supplied  with  hot  water  jackets. 
In  order  to  free  the  crystals  as  thoroughly  as  possible  from  adhering 
mother  liquor,  they  were  placed  in  a hard  rubber  funnel  and  swung  through 
the  air  as  rapidly  as  possible  in  a circle  having  a diameter  of  nearly  three 
meters,  and  the  drainings  were  allowed  to  collect  in  a tube  of  hard  rubber. 
This  method  of  draining  crystals,  which  has  been  described  by  Richards,^ 
proved  very  effective  with  this  salt  as  the  crystals  were  in  the  form  of 
needles  which  did  not  easily  retain  the  mother  liquor  between  their  points 
of  contact,  as  would  have  been  the  case  with  the  fluoxycolumbate  of 
potassium,  which  crystallizes  in  thin  flexible  leaflets. 

The  first  crops  of  crystals  obtained  from  the  various  crystallizations 
were  as  follows: 

From  the  first  crystallization,  8.5  kilograms. 

From  the  second  crystallization,  3 . 4 kilograms. 

From  the  third  crystallization,  2 . 2 kilograms. 

From  the  fourth  crystallization,  1.5  kilograms  (crystals  A). 

^ This  Journal,  27,  no  (1905). 


OBSERVATIONS  ON  COLUMBIUM. 


1639 


By  a further  recrystallization  of  the  second  and  third  crops  of  crystals, 
obtained  upon  concentrating  the  mother  liquors  from  the  third  and  fourth 
crystallizations  mentioned  above,  four  kilograms  of  salt  (crystals  B) 
were  obtained,  which  were  fully  as  pure  as  crystals  A. 

In  order  to  test  this  salt  for  tin  and  tungsten  200  grams  of  crystals  A 
were  decomposed  with  sulphuric  acid,  and  the  oxide  obtained  was  fused 
with  sodium  carbonate  and  sulphur.  The  soluble  portion  of  the  fusion 
was  treated  with  dilute  hydrochloric  acid  and  the  sulphur,  which  would 
have  contained  the  tin  and  tungsten,  was  burned  in  a weighed  porcelain 
crucible.  The  residue  obtained  amounted  to  0.001  per  cent,  of  the  weight 
of  the  salt  taken.  It  was  therefore  concluded  that  the  crystallizations 
had  removed  these  impurities  from  the  material.  The  oxide,  however, 
still  gave  a color  reaction  with  hydrogen  peroxide  corresponding  to  about 
0.15  per  cent,  of  its  weight  in  titanium  dioxide. 

The  salt  contained  an  appreciable  quantity  of  potassium  tantalum 
fluoride  which  was  removed  by  baking  the  double  fluoride  as  indicated 
by  Hall  and  Smith.  Crystals  A,  to  the  amount  of  1.3  kilograms,  were 
brought  into  solution  in  a large  platinum  dish  and  the  solution  was  boiled 
for  several  days.  Targe  quantities  of  hydrofluoric  acid  escaped,  the 
potassium  columbium  fluoride,  K2CbF7,  changing  into  fluoxycolumbate 
of  potassium,  K2Cb0F5.H20.  The  latter  was  finally  baked  for  several 
hours,  then  dissolved  in  water,  and  the  resulting  solution  filtered  through 
a rubber  funnel  supplied  with  a hot- water  jacket.  This  operation  was 
repeated  until  the  insoluble  residue,  when  dissolved  in  a small  amount 
of  hydrofluoric  acid,  showed  only  the  solubility  of  potassium  columbium 
oxyfluoride.  In  making  this  test  the  solution  was  evaporated  to  dry- 
ness two  or  three  times,  so  that  the  solubility  of  the  salt  in  pure  water 
could  be  noted. 

A possible  trace  of  silica  was  removed  as  usual  by  decomposing  the 
double  fluoride  with  sulphuric  acid.  A large  excess  of  acid  was  used 
and  the  heating  was  continued  until  the  mass  was  dry  and  contained 
comparatively  little  free  acid.  The  oxide  obtained  on  treating,  this  mass 
with  water  was  washed  many  times  in  a large  platinum  dish  by  decanta- 
tion. A portion  of  this  oxide  after  several  hours’  ignition  over  a good 
burner  showed  a specific  gravity  of  4.8. 

Inasmuch  as  this  oxide,  which  we  had  reason  to  believe  was  free  from 
titanium,  still  gave  a color  reaction  with  hydrogen  peroxide,  there  seemed 
to  be  no  further  doubt  that  this  reaction  was  due  to  columbium  itself. 
The  one  other  possible  interpretation  would  necessitate  the  assumption 
that  some  other  element  was  still  present  in  the  columbium,  which  had 
not  been  removed  by  the  treatments  indicated  above.  In  order  to  further 
test  this  point,  portions  of  the  oxide  were  converted  into  chloride,  and 
the  latter  carefully  fractionated,  the  various  fractions  being  examined 


1640  CIvARENCE  W.  BALKE  AND  EDGAR  F.  SMITH. 

as  to  their  composition,  their  vapor  density,  and  the  specific  gravity  of 
the  oxides  obtained  on  treating  the  chloride  with  water  or  ammonium 
hydroxide. 

Preparation  of  Columhium  Chloride. — The  chloride  was  obtained  by 
using  the  method  first  suggested  by  Smith  and  Hall,^  which  consisted 
in  the  ignition  of  columbium  oxide  in  the  vapor  of  sulphur  monochloride 
and  a final  distillation  of  the  product  in  an  atmosphere  of  chlorine  gas. 
The  apparatus  used  by  us  is  indicated  in  Fig.  i.  The  bulb  A contained 


Fig.  I. — Apparatus  used  for  the  preparation  of  columbium  chloride. 


the  sulphur  monochloride,  and  the  tube  D served  for  the  introduction 
of  dry  chlorine.  Strongly  ignited  columbium  oxide,  in  quantities  of 
10-20  grams,  was  placed  in  the  tube  E,  and  the  latter  then  moderately 
heated  with  a series  of  four  fish-tail  burners.  On  passing  the  vapor  of 
sulphur  monochloride,  the  voluminous  oxychloride  of  columbium  was 
formed,  but  the  latter  was  gradually  converted  into  the  chloride,  which 
together  with  the  excess  of  sulphur  monochloride  collected  in  bulb  F. 
Great  care  was  required  to  prevent  the  obstruction  of  the  apparatus 
by  the  columbium  oxychloride,  and  constant  attention  was  required 
until  the  very  completion  of  the  experiment.  The  tube  E was  very 
liable  to  crack,  due  to  the  condensation  of  sulphur  monochloride  on  the 
heated  glass,  so  that  it  was  found  advisable  to  make  the  tube  as  short 
as  possible,  and  to  protect  the  anterior  end  of  the  tube  E with  asbestos 
paper.  It  was  also  found  desirable  to  pass  dry  chlorine  into  the  apparatus 
during  the  entire  experiment.  When  the  desired  quantity  of  oxide  had 
been  converted  into  chloride,  which  required  from  ten  to  twenty  hours, 
the  stopcock  a was  closed  and  the  excess  of  sulphur  monochloride  was 
driven  through  the  bulbs  H and  I and  collected  in  K.  The  columbium 
chloride  was  then  distilled  from  F into  H,  and  finally  from  H into  I. 
It  was  found  to  be  comparatively  easy  to  remove  the  sulphur  monochlo- 
ide  completely  by  these  distillations.  The  bulb  I was  finally  sealed  off 
at  c and  e. 

The  apparatus  used  for  the  fractionation  of  the  chloride  is  pictured 

^ This  Journal,  26,  1235  (1904). 


OBSERVATIONS  ON  COLUMBIUM. 


1641 


in  Fig.  2.  The  bulb  I was  connected  with  bulb  L by  means  of  the  adapter 
N.  A rubber  stopper  was  used  to  make  the  connection,  and  the  bulb 
I was  adjusted  as  rapidly  as  possible  after  breaking  off  the  ends  of  the 
side  tubes,  and  a rapid  stream  of  chlorine  was  immediately  passed  through 


Fig.  2. — Apparatus  used  for  the  fractionation  of  columbium  chloride. 


the  apparatus.  The  chloride  was  then  distilled  into  bulb  T,  and  from 
this  bulb  it  was  carefully  distilled  into  the  smaller  bulbs  in  such  a manner 
as  to  make  the  fractionation  as  effective  as  possible.  At  the  conclusion 
of  the  fractionation  the  long  tube  T was  sealed  off  at  m and  n,  and  finally 
the  individual  bulbs  were  sealed  off  at  their  constrictions. 

The  chloride  thus  obtained  had  a beautiful  sulphur-yellow  color  when 
in  the  solid  state,  but  when  fused  its  color  was  red.  On  solidifying  it 
contracted  appreciably,  shrinking  away  from  the  walls  of  the  containing 
bulb.  This  was  found  to  be  a great  advantage  in  removing  the  chloride 
for  analysis,  as  it  was  an  easy  matter  to  shake  it  into  pieces  small  enough 
to  pass  through  the  neck  of  the  small  bulbs. 

Three  preparations  of  columbium  chloride  were  made  and  fractionated 
by  this  method. 

Oxide  used.  Number  of  bulbs  in 


Preparation.  Grams.  fractionating  apparatus. 

1 50  10 

II 60  15 

III 90  21 


The  bulb  L of  the  fractionating  apparatus  used  for  the  third  preparation 
carried  a thermometer  which  was  sealed  within  a glass  tube  at  the  top 
of  the  bulb.  The  entire  quantity  of  chloride  distilled  at  a temperature 
varying  but  slightly  from  241°.  The  columbium  chloride  had  a marked 
tendency  to  volatilize  at  a temperature  much  below  its  boiling  point, 
and  the  vapors  condensed  in  the  cooler  parts  of  the  apparatus  in  beauti- 
ful yellow  needles.  In  all  of  the  preparations  the  chloride  collected  in 


1642 


CI.ARKNCE  W.  BALKE  AND  E)DGAR  R.  SMITH. 


the  last  three  or  four  bulbs  of  the  fractionating  apparatus  consisted  wholly 
of  this  sublimed  material,  and  it  surely  would  have  contained  appreciable 
amounts  of  any  chloride  more  volatile  than  columbium  chloride  had 
such  been  present  in  the  latter  at  the  beginning  of  the  fractionation. 
It  may  be  said  here  in  anticipation  of  the  results  which  follow  that 
no  differences  could  be  detected  between  any  of  the  fractions  obtained. 

A portion  of  the  oxide  obtained  from  this  chloride  has  been  carefully 
examined  spectroscopically  by  Joel  H.  Hildebrand,  of  this  laboratory. 
A careful  measurement  of  the  wave  lengths  of  the  lines  obtained  with 
a five-foot  concave  grating  did  not  reveal  the  presence  of  any  titanium 
or  tantalum  lines.  Tantalum  oxide,  purified  by  the  method  previously 
described  by  one  of  us,^  was  converted  into  chloride  and  fractionated  as 
described  above,  and  the  oxide  obtained  therefrom  was  also  examined 
by  Hildebrand,  with  the  result  that  no  titanium  or  columbium  lines  ap- 
peared. 

Vapor  Density  of  Columbium  Chloride. — A number  of  determinations 
of  the  vapor  density  of  columbium  chloride  were  made,  using  the  method 
of  Dumas.  The  bath  used  consisted  of  a mixture  of  fused  potassium  and 
sodium  nitrates.  The  side  tubes  of  100  cc.  distilling  bulbs  were  sealed 
11  off,  and  after  being  thoroughly  cleaned  and  dried,  an 
I ample  quantity  of  the  chloride  was  introduced  and  the 
neck  of  the  bulb  was  loosely  stoppered.  The  latter  was 
then  drawn  out  to  the  form  shown  in  Fig.  3.  After 
p the  vaporization  of  the  chloride,  the  bulb  was  sealed 

J off  at  a.  It  was  found  impracticable  to  seal  off  the  tip 

/ \ capillary  tube,  as  is  usually  done,  as  a deposit 

I of  columbium  oxide  formed  on  the  latter  which  pro- 

\ j duced  an  enamel  with  the  glass  very  difficult  of  fusion. 

After  the  bulb  had  been  weighed,  its  tip  was  broken 
off  under  water  and  the  amount  of  residual  air  deter- 
mined.  The  columbium  hydroxide  was  dissolved  out 
of  the  bulb  with  a hot  solution  of  potassium  binoxalate  and  the  glass 
weighed.  The  bulb  was  finally  filled  with  water  and  weighed  as  usual. 
In  making  the  calculations,  all  necessary  corrections  were  applied. 


Temperature  Wt.  CbCls  Wt.  of  equal 

Series.  Bulb.  of  bath.  (vac.).  vol.  of  air.  Density. 

I.... 6 280°  0.8026  0.08495  9-45 

I 6 300°  0.7098  0.07575  9-37 

II 5 292°  0.8379  0.08989  9.32 

III I 275°  0.8333  0.08702  9.58 

III 20  280°  0.7551  0.07931  9.52 


Mean,  9.45 

The  calculated  density,  using  93.5  as  the  atomic  weight  of  columbium, 
^ This  Journal,  27,  1140  (1905). 


OBSERVATIONS  ON  COEUMBIUM.  1 643 

is  9.35.  Deville  and  Troost  ^ obtained  the  value  9.6.  It  will  be  observed 
that  in  Series  III  the  chloride  from  the  extreme  fractions  gave  prac- 
tically the  same  vapor  density. 

After  the  completion  of  the  third  preparation  of  columbium  chloride, 
the  small  amount  of  the  latter  which  had  passed  over  into  bulb  K with 
the  sulphur  monochloride  was  recovered  by  decomposing  the  latter  with 
water  and  burning  the  sulphur.  The  small  quantity  of  oxide  thus  ob- 
tained was  converted  into  a double  fluoride  with  potassium. 

On  analysis  2.1000  grams  of  this  salt  gave  0.9368  gram  of  oxide  and  1.2223  grams 
of  K2SO4,  or  44.61  per  cent,  of  oxide  and  58.20  per  cent,  of  K2SO4.  The  salt  was, 
therefore,  the  fluoxycolumbate  of  potassium  which  requires  44.38  per  cent,  of  CbgOs 
and  57.94  per  cent,  of  K2SO4. 

Density  of  Columbium  Oxide. — The  value  obtained  for  the  density  of 
columbic  oxide  depended  largely  on  its  method  of  preparation.  It  is 
worthy  of  note  that  the  density  of  the  oxide  obtained  by  igniting  the 
precipitate  resulting  from  the  treatment  of  columbium  chloride  with 
dilute  ammonium  hydroxide  was  always  about  half  a unit  lower  than 
that  observed  when  the  oxide  was  obtained  by  allowing  the  chloride  to 
decompose  in  a moist  atmosphere.  From  the  results  obtained  it  would 
appear  that  a determination  of  the  density  of  columbic  oxide,  obtained 
by  these  methods,  would  be  of  little  value  as  a means  of  detecting  the 
presence  of  small  quantities  of  an  admixed  oxide.  The  following  values 
were  obtained  for  the  oxide  prepared  by  the  first  method  mentioned 
above:  oxide  made  from  the  chloride  in  bulb  10,  Series  I,  4.51;  bulb  3, 
Series  I,  4.48.  When  the  second  method  was  used  in  the  preparation  of 
the  oxide,  the  following  results  were  obtained:  bulb  10,  Series  II,  4.93; 
bulb  13,  Series  II,  4.88;  bulb  i.  Series  I,  5.05;  bulb  17,  Series  III,  5.02. 

Density  of  Columbium  Chloride. — The  only  liquids  which  were  found 
to  be  satisfactory  for  use  in  a determination  of  the  specific  gravity  of 
columbium  chloride  were  sulphur  monochloride  and  carbon  tetrachloride. 
The  others  which  were  tried  either  dissolved  or  decomposed  the  chloride. 
While  columbium  chloride  dissolves  quite  readily  in  hot  sulphur  mono- 
chloride and  carbon  tetrachloride,  it  is  but  slightly  soluble  in  these  com- 
pounds at  the  ordinary  temperature.  In  order  to  obtain  as  great  ac- 
curacy as  possible,  these  liquids  were  saturated  with  columbium  chloride 
at  20°  C.  and  the  solutions  were  used  in  the  determinations.  With  sul- 
phur monochloride  the  following  data  were  obtained: 


Wt.  of  columbium  chloride 5.4442 

Wt.  of  pycnometer 6.6145 

Wt.  of  pycnometer  + water 17.2756 

Wt.  of  pycnometer  + SgCb 24.5750 

Wt.  of  pycnometer  SgCb  + CbClg 26.7135 

t=  20°  C. 


Specific  gravity  of  columbium  chloride  = 2.77. 
^ Compt.  rend.^  56,  891  (1863), 


1644  CLARENCE  W.  BALKE  AND  EDGAR  F.  SMITH. 

A similar  experiment  in  which  carbon  tetrachloride  and  7.07  grams 
of  columbium  chloride  were  used  gave  the  value  2.73. 

The  Atomic  Weight  of  Columbium. 

(See  Clarke,  “Recalculation  of  the  Atomic  Weights,  Smithsonian  Mis- 
cellaneous Collections,”  1897.) 

Of  the  previous  determinations  of  the  atomic  weight  of  columbium 
those  made  by  Rose,  Hermann,  and  Blomstrand  seem  to  be  without 
present  value,  while  the  determinations  of  Marignac  are  far  from  satis- 
factory. Rose  ^ analyzed  a compound  which  he  thought  to  be  chloride, 
but  which  was  probably  oxychloride,  in  which  case  his  value  becomes 
nearly  94.  The  results  obtained  by  Hermann^  need  not  be  considered, 
while  those  of  Blomstrand®  are  very  discordant.  The  latter  chemist 
analyzed  columbium  chloride,  weighing  the  columbium  as  the  pentoxide 
and  the  chlorine  as  silver  chloride.  There  is  a difference  of  nearly  four 
units  between  the  lowest  and  highest  value  for  the  atomic  weight  of 
columbium  as  calculated  from  the  percentages  of  columbic  oxide,  and 
similar  variations  in  the  value  appear  when  the  latter  is  calculated  from 
the  ratios  5 AgCl : CbClj  and  5 AgCl : CbaOj.  Blomstrand  also  analyzed  a 
sodium  columbate,  but  his  results  in  this  connection  are  valueless  in  that 
they  indicate  the  value  of  the  atomic  weight  of  columbium. 

The  accepted  value  for  the  atomic  weight  of  columbium  is  obtained 
from  the  investigations  of  Marignac.^  This  chemist  made  about  twenty 
analyses  of  the  potassium  fluoxycolumbate,  2KF.CbOF3.H2O.  The  fol- 
lowing percentages  were  obtained: 


CbjOfi Extremes  44.15  to  44 . 60 

KjS04 Extremes  57 . 60  to  58 .05 

HjO Extremes  5 . 75  to  5.98 

F Extremes  30.62  to  32.22 

Using  the  values  O = 16,  K = 39.15,  F = 19  and  H = i.oi,  we  obtain 


from  the  extreme  percentages  of  Cb205  the  values  92.27  and  94.70  for 
the  atomic  weight  of  columbium.  In  like  manner,  from  the  extreme 
percentages  of  K2SO4,  we  obtain  the  values  95.38  and  93.04.  In  other 
words  there  is  a difference  of  over  three  units  between  the  highest  and 
lowest  values  obtained  by  Marignac. 

Pure  columbium  chloride  having  been  obtained  in  large  quantities,  it  was 
determined  to  use  this  compound  in  a redetermination  of  the  atomic 
weight  of  columbium.  The  ratio  between  columbium  chloride  and 
columbium  oxide  was  investigated.  The  following  is  an  account  of  the 
analytical  method  employed : 

' Pogg.  Ann.,  104,  439  (1858). 

* J.  prakt.  Chent.,  68,  73  (1856). 

^Acta  Univ.  Lund,  1864. 

* Arch.  set.  phys.  nat.  [2],  23  (1865). 


OBSERVATIONS  ON  COEUMBIUM. 


1645 

By  carefully  tapping  one  of  the  bulbs  containing  the  columbium  chloride, 
the  latter  was  broken  up  into  small  pieces;  the  neck  of  the  bulb  was  then 
broken  off,  and  the  chloride  quickly  transferred  to  a carefully  cleaned 
and  dry  glass-stoppered  weighing  bottle  of  such  size  as  to  be  nearly  filled 
with  the  amount  of  chloride  employed.  After  carefully  weighing  the 
bottle,  the  chloride  was  transferred  to  a previously  tared  porcelain  crucible, 
and  the  bottle  was  again  weighed.  The  covered  crucible  was  placed 
in  a desiccator  containing  water,  and  allowed  to  stand  two  or  three  days. 
The  chloride  was  gradually  converted  into  oxide,  and  when  this  was 
complete,  the  crucible  was  half  filled  with  water  and  transferred  to  a 
water  bath  supplied  with  porcelain  rings.  In  order  to  exclude  dust  a 
large  glass  funnel  was  suspended  over  the  crucible.  When  the  mass 
had  become  nearly  dry,  a small  amount  of  water  and  several  drops  of 
pure  nitric  acid  were  added,  and  the  evaporation  continued  to  dryness. 
It  was  found  desirable  to  complete  the  final  evaporation  with  the  lid  in 
place,  as  a slight  decrepitation  was  noticed  as  the  oxide  dried  on  the  walls 
of  the  crucible.  It  was  also  found  convenient  to  use  a lid  which  was 
small  enough  to  rest  within  the  upper  edge  of  the  crucible.  When  the 
mass  had  become  thoroughly  dry,  the  resulting  oxide  was  carefully  ig- 
nited. Great  care  was  necessary  at  this  point,  as  the  oxide  had  a tendency 
to  decrepitate  slightly,  accompanied  with  a possible  loss  of  material 
in  the  form  of  a fine  dust.  On  ignition  the  mass  became  brown  in  color, 
oxides  of  nitrogen  were  expelled,  and  as  the  temperature  was  increased, 
the  oxide  took  on  the  characteristic  pale  yellow  color  of  ignited  columbium 
oxide.  The  crucible  was  finally  heated  to  constant  weight  with  a good 
blast,  the  heat  being  applied  for  fifteen  minutes  between  each  weighing. 

In  the  preliminary  experiments  nitric  acid  was  not  used  and  the  results 
obtained  were  too  low,  due  to  a volatilization  of  a small  amount  of  colum- 
bium oxide.  White  fumes  escaped  from  the  crucible  and  a sublimate 
formed  on  the  under  side  of  the  crucible  lid*  Columbium  oxide  is  known  to 
form  a volatile  body  when  ignited  in  an  atmosphere  of  hydrogen  chloride.^ 
The  use  of  a small  amount  of  nitric  acid  seemed  to  effectively  prevent 
this  action,  the  hydrochloric  acid  being  expelled  before  the  temperature 
became  high  enough  to  form  a volatile  body. 

The  exposure  of  columbium  chloride  to  the  air  may  be  pointed  out  as 
a serious  objection  to  this  method  of  analysis.  In  order  to  test  this  point, 
a weighing  bottle  containing  some  of  the  chloride  was  carefully  w’eighed 
and  then  allowed  to  remain  with  the  stopper  removed  for  a length  of  time 
comparable  with  that  required  to  transfer  the  material  in  the  determi- 
nation. On  reweighing  the  bottle  its  loss  in  weight  was  found  to  be 
about  0.00002  gram.  It  will  thus  be  seen  that  the  error  involved,  while 
objectionable,  is  not  serious.  When  columbium  chloride  is  exposed  to 
^ Smith  and  Maas,  Z.  anorg.  Chem.,  7,  96  (1894),  and  Hall  and  Smith. 


1646 


CIvARHNCK  W.  BALKE  AND  KDGAR  F.  SMITH. 


the  air  it  at  once  becomes  coated  with  a film  of  white  oxide.  This  change 
can  easily  be  detected  with  the  eye  before  it  would  be  noticed  on  the 
balance.  With  a little  experience  it  was  possible  to  transfer  the  chloride 
to  the  weighing  bottle  without  the  formation  of  such  a coating. 

Nearly  all  of  the  weighings  were  made  by  substitution,  and  the  weights 
were  standardized  by  the  method  devised  by  Richards.^  In  making 
the  calculations  the  following  atomic  weights  were  used:  O = 16  and 
Cl  = 35.45.  In  making  the  corrections  to  the  vacuum  standard  the 
following  densities  were  employed:  CbClg  = 2.75,  Cb205  = 5.00  and 
weights  = 8.4.  The  results  obtained  are  contained  in  the  following  table: 


Sample  used. 
Series.  Bulb. 

wt.  CbClfi 
(vac.) . 

Wt.  CbaOs 
(vac.). 

Parts  Cb205 
to  100.000 
parts  CbCls. 

At  wt.  of 
columbium. 

II 

I 

9-56379 

4-71539 

49-305 

93-49 

II 

2 

5-42742 

2.65730 

49.292 

93-42 

III 

3 

5-15992 

2.54364 

49.296 

93-44 

III 

16 

9.64854 

4.75641 

49-297 

93-44 

II 

8 

7-24572 

3.57222 

49-301 

93-47 

I 

7 

8.00559 

3-94746 

49  309 

93-51 

I 

8 

9-60763 

4-73852 

49-324 

93-58 

II 

10 

9.19732 

4-53638 

49-323 

93-58 

63-85593 

31-48532 

49.307 

93-50 

An  attempt  was  made  to  determine  the  atomic  value  from  the  ratio 
CbClg  : 5AgCl,  by  decomposing  the  columbium  chloride  with  dilute 
ammonium  hydroxide,  acidifying  the  solution  with  nitric  acid,  filtering 
out  the  columbium  hydroxide,  and  determining  the  chlorine  in  the  filtrate 
as  silver  chloride.  Several  determinations  were  made,  but  the  results 
obtained  were  not  satisfactory.  It  was  extremely  difficult  to  wash  out 
the  last  traces  of  chloride  from  the  columbium  hydroxide.  In  one  of 
these  determinations  the  columbium  hydroxide  was  carefully  collected, 
dried,  and  ignited  to  oxide  in  a weighed  platinum  crucible,  with  the 
following  results: 

Wt.  CbClfi  Wt.  CbsOs  Parts  CbgOe  to  At.  wt.  of 

Series.  Bulb.  (vac.).  (vac.).  loo.ooo  parts  CbCls-  columbium. 

Ill  13  4-27456  2.10734  49-300  93-46 

These  results  indicate  that  the  atomic  weight  of  columbium  as  given 
in  the  International  Table  is  probably  too  high.  Accordingly,  the  value 
93.5  has  been  used  in  the  calculations  contained  in  the  present  paper. 

Columbates. 

Historical. — ^The  solubility  of  the  fused  mass  obtained  by  heating  a 
mixture  of  columbite  or  tantalite  with  sodium  or  potassium  carbonate 
was  recognized  by  the  very  first  investigators  of  these  minerals.  Gehlen^ 

^ This  Journal,  22,  144  (1900). 

* Schweigger’s  J.  Chem.  Physik.,  6,  258  (1812). 


OBSERVATIONS  ON  COLUMBIUM. 


1647 

obtained  small  soluble  crystals  from  the  solution  of  such  a fusion,  but 
the  first  systematic  investigation  of  these  bodies  was  made  by  H.  Rose.^ 

In  considering  Rose’s  work  it  must  be  borne  in  mind  that  the  material 
which  he  used  in  the  preparation  of  the  various  columbates  was  more 
or  less  impure,  and  probably  always  contained  varying  amounts  of  tan- 
talum. He  considered  the  columbates  to  be  derivatives  of  “unter- 
niobsaure,”  Cb20g,  and  after  Marignac  had  shown  that  columbic  acid 
was  CbgOg,  Rammelsberg^  recalculated  Rose’s  results,  and  the  formulas 
obtained  are  given  below. 

Nafi.Ch^O^.6  or  gH^O. — Rose  described  this  salt  as  being  the  best 
crystallized  and  the  most  stable  of  all  the  salts  of  tantalic  or  columbic 
acids.  It  was  prepared  by  fusing  columbic  oxide  (obtained  by  heating 
columbite  with  acid  potassium  sulphate,  or  by  decomposing  columbium 
chloride),  an  acid  sodium  columbate  or  columbium  hydroxide  with  so- 
dium hydroxide  in  a silver  crucible.  A clear  fusion  did  not  result,  and  on 
treating  the  mass  with  water,  a residue  was  obtained  insoluble  in  an 
excess  of  sodium  hydroxide,  but  soluble  in  water.  The  neutral  sodium 
columbate  was  again  obtained  when  this  solution  was  added  to  a solution 
of  sodium  hydroxide.  This  salt  was  also  got  by  heating  a solution  of 
sodium  hydroxide  containing  columbium  hydroxide  in  suspension.  The 
latter  did  not  dissolve,  but  after  the  removal  of  the  excess  of  sodium  hy- 
droxide, the  residue  was  soluble  in  water  and  on  evaporating  this  solu- 
tion the  salt  was  obtained  in  a crystalline  form.  Finally,  Rose  obtained 
this  salt  by  fusing  columbic  oxide  with  sodium  carbonate.  The  fused 
mass  was  treated  with  water  and  the  residue,  insoluble  in  the  excess  of 
alkaline  carbonate,  was  dissolved  in  water,  the  solution  being  allowed 
to  stand  for  a long  time,  when  on  evaporating  the  clear  liquid  the  neutral 
salt  often  separated  in  crystalline  form.  The  following  analytical  results 
were  obtained ; 


Calculated. 

Pound  (mean). 

Calculated. 

Found. 

Cb20s . . 

. . 268 

61.20 

60.82 

Cb^O,.. 

. . 268 

54-47 

54-05 

Na^O  . . 

. . 62 

14.16 

15.86 

Na^O  . . 

. . 62 

12.60  • 

14.40 

6H2O  . . 

. . 108 

24.64 

9H2O  . . 

. . 162 

32.93 

438 

100.00 

492 

100.00 

jA'agO. 2C62O5. 24/^2^ • — 'I'his  salt  was  obtained  but  once  during  the 
preparation  of  the  preceding  salt. 

sNafi.Cbfi^. — As  calculated  from  the  amount  of  carbon  dioxide  ex- 
pelled, Rose  concluded  that  this  salt  was  formed  when  columbic  oxide 
was  fused  for  a long  time  with  sodium  carbonate.  When  treated  with 
water  it  was  decomposed  into  the  neutral  salt  and  sodium  hydroxide. 

^ Pogg.  Ann.,  113,  105  and  292  (1861). 

* Jour,  fur  Chem.,  108,  77  (1869). 


1648 


CI.ARENCK  W.  BALKB  and  KDGAR  R.  SMITH. 


4Nafi.5Ch20^.4oH^0. — ^This  salt  was  obtained  by  fusing  columbic 
oxide  with  sodium  carbonate  at  a low  temperature. 

N a.p. 40)20 — This  compound  was  obtained  as  a gelatinous  pre- 
cipitate on  conducting  carbon  dioxide  into  a solution  of  the  neutral  salt. 

{^/ 6NH^.i / 6Na)2p.4O20^.5H20 . — Rose  obtained  this  body  as  a volu- 
minous precipitate  on  adding  an  ammonium  salt  to  a solution  of  the  neutral 
sodium  columbate.  Other  columbates  obtained  by  him  were  these : 


2Fe203-3Cb205.8H20 

Rose  did  not  succeed  in  preparing  crystalline  potassium  columbates 
but  from  the  amount  of  carbon  dioxide  expelled  on  fusing  columbic 
oxide  with  potassium  carbonate,  he  concluded  that  3K20.Cb205  was 
present  in  the  fusion. 

Marignac^  was  unable  to  obtain  definite  sodium  salts  of  columbic  acid, 
but  he  obtained  a number  of  potassium  columbates: 

4K20.3O2P^.i6H20. — This  salt  was  obtained  by  fusing  columbic 
oxide  with  potassium  carbonate,  the  aqueous  solution  of  the  melt  deposit- 
ing the  salt  in  well  defined  crystals. 

8K2P.yO20^.32H20. — This  formula  was  assigned  by  Marignac  to  the 
salt  obtained  by  recrystallizing  the  preceding  salt  from  pure  water. 

3K20 .2020^.1 1 H 2O . — This  salt  was  obtained  in  well  defined  crystals 
when  the  last-mentioned  salt  was  recrystallized  from  an  excess  of  caustic 
potash. 

Nq20.3K20 .3020^.9 H2O. — Marignac  obtained  this  body  as  a white, 
pulverulent  mass  on  adding  potassium  hydroxide,  containing  some  sodium 
hydroxide,  to  a solution  of  the  first  salt.  It  was  insoluble  in  the  alkaline 
liquor  and  but  slightly  soluble  in  water. 

K20- 301)20 ^.3H20. — This  salt  was  precipitated  on  boiling  a solution 
of  potassium  fluoxycolumbate  with  potassium  bicarbonate.  It  was 
insoluble  in  water. 

Hermann^  described  a number  of  columbates  of  potassium  and  sodium, 
but  his  work  cannot  be  considered  of  great  present  value.  On  adding 
sodium  hydroxide  to  a hot  solution  of  potassium  fluoxycolumbate,  he 
obtained  a body  to  which  he  assigned  the  composition  5Na20. 40^265.- 
21H2O. 

Santesson^  obtained  the  salt  K20.2Cb205.5F2H20  by  fusing  the  cal- 
culated amount  of  potassium  carbonate  with  columbic  oxide.  It  was 
insoluble  in  water.  When  a large  excess  of  potassium  carbonate  was 
used,  he  obtained  the  salt  2K2O.Cb2O5.nH2O  as  a residue  after  extracting 

^ Bibl.  Univ.,  Archives,  23,  249  (1865);  Jour,  fiir  Chem.,  97,  449  (1866). 

2 Jour,  fur  Chem.,  iii,  373  (1871). 

^ Bull.  soc.  chim.  [2],  24,  52. 


4AgCb03.H20 

CuO.Cb2O5.2H2O 


MgO.Cb2O5.4H2O 

Hg2O.Cb2O5.3H2O 


OBSERVATIONS  ON  COEUMBIUM. 


1649 


the  fusion  with  water.  The  salt  Na2O.Cb2O5.6H2O  was  soluble  in  water, 
while  the  salt  2Na2O.3Cb2O5.9H2O,  obtained  by  fusing  the  last  salt 
mentioned  with  sodium  hydroxide,  was  insoluble  in  water. 

A.  Joly^  obtained  a number  of  salts  by  heating  columbic  oxide  with 
a metallic  chloride  at  a temperature  somewhat  below  that  at  which  the 
chloride  volatilized.  At  times  the  chloride  was  replaced  by  a mixture 
of  the  metallic  fluoride  and  an  alkali  chloride.  He  obtained  the  following: 
4Mg0.Cb205  2Ca0.Cb20s  FeO.Cbp^ 

3Mg0.Cb20g  Ca0.Cb205  MnO.CbaOg  . 

3Y0.Cb203 

No  analyses  of  these  bodies  are  given. 

Larsson^  prepared  a number  of  bodies  by  recrystallizing  the  precipitated 
amorphous  columbates  from  the  fused  chloride  of  the  corresponding 
metal,  or  from  boron  trioxide.  The  compounds  given  under  I.  were 
obtained  when  the  fused  metallic  chlorides  were  used,  and  those  under 
II.  were  obtained  when  boron  trioxide  was  employed. 


I.  II. 


4Mg0.Cb205 

MgO.CbjOj 

aCaO.CbjOj 

CaO.CbjOj, 

YjOjCbjOs 

CuO.CbjOs 

ZnO.Cb^Oj 

CdO.CbjOj 

CoO.Cb^O, 

SMnO.sCbA 

sThOj.ibCbjO, 

ZrOj-sCbjO, 

All  of  these  salts  are  described  as  being  crystalline  in  nature.  All 
of  the  amorphous  precipitates  were  obtained  from  potassium  columbate. 
Larsson  could  not  obtain  the  magnesium  salt,  3Mg0.Cb205,  described 
by  Joly. 

P.  J.  HolmquisH  obtained  a crystalline  salt,  NaCbOg,  by 'fusing  to- 
gether columbic  oxide,  sodium  carbonate  and  sodium  fluoride  (the  last 
being  used  as  a flux),  which  he  described  as  being  insoluble  in  water  and 
acids.  He  also  obtained  a pure  calcium  pyrochlore  to  which  he  gave 
the  formula  NaCaCbOgF. 

Bedford^  obtained  a sodium  columbatejto  which  was  assigned  the  com- 
position 7Na20.6Cb205.32H20,  by  recrystallizing  the  sodium  columbate, 
obtained  on  adding  sodium  hydroxide  to  a hot  solution  of  potassium 

^ Compt.  rend.,  61,  266  (1875). 

2 Z.  anorg.  Chem.,  12,  188  (1896). 

^ Bull.  geol.  Instil.  Upsala,  3,  Nr.  5;  Z.  anorg.  Chem.,  18,  84  (1898). 

* Thesis,  Univ.  of  Penna.,  1905;  This  Journal,  27,  1216  (1905). 


1650  CIvARENCK  W.  BARKE  AND  EDGAR  R.  SMITH. 

fluoxycolumbate  (Hermann’s  method).  The  same  salt  was  prepared 
by  fusing  columbic  oxide  with  sodium  hydroxide  and  recrystallizing 
the  product,  which  was  insoluble  in  the  excess  of  alkali,  from  pure  water. 
When  columbic  oxide  was  fused  with  sodium  carbonate,  and  the  resulting 
sodium  columbate  was  dissolved  in  pure  water  and  the  solution  added 
to  one  of  sodium  carbonate,  the  same  salt  (with  36H2O)  separated  as 
a fine  powder.  From  a solution  of  the  sodium  salt  the  following  were 
obtained  as  amorphous  precipitates: 

7Ba0.6Cb205.i8H20  7Zn0.6Cb205.25H20 

7Ag2O.6Cb2O5.5H2O 

Experimental. — In  general,  columbates  of  the  alkali  metals  were  ob- 
tained by  fusing  columbium  oxide  with  the  alkali  carbonates.  The  prod- 
ucts obtained  depended  in  part  upon  the  relative  quantities  of  oxide 
and  carbonate  used.  When  too  small  an  amount  of  carbonate  was 
employed  insoluble  acid  columbates  were  produced,  while  the  use  of 
ample  quantities  of  potassium,  rubidium,  or  cesium  carbonates  gave 
perfectly  clear  fusions  which  were  completely  soluble  in  small  amounts 
of  water.  However,  when  sodium  carbonate  was  used  a clear  fusion 
was  not  obtained,  and  the  resulting  columbate  was  not  soluble  in  the 
presence  of  the  excess  of  alkali  carbonate,  but  dissolved  completely  in 
pure  water. 

Analysis:  The  water  of  crystallization  was  determined  as  loss  on  igni- 
tion. The  columbic  acid  was  precipitated  from  solutions  of  the  alkali 
columbates  by  the  addition  of  sulphuric  acid,  and  the  alkali  metal  was 
determined  as  sulphate  in  the  filtrate.  Exceptions  to  this  method  of 
analysis  will  be  noted  under  the  individual  salts. 

I : I Columbates. — In  order  to  obtain  a sodium  columbate  to  serve  in 
the  preparation  of  a sodium  percolumbate,  recourse  was  had  to  the  method 
of  Hermann  as  outlined  by  Bedford  in  his  study  of  the  7 : 6 sodium  colum- 
bate. A large  quantity  of  this  salt  was  prepared  and  recrystallized  twice 
from  water.  A sample  of  this  salt  gave  the  following  results  on  analysis: 
0.6896  gram  of  salt  lost  0.1490  gram  on  ignition,  corresponding  to  21.61  per  cent. 
H2O. 

0.9169  gram  of  salt  gave  0.5652  gram  of  CbgOj  and  0.3542  gram  of  Na2S04,  or 
61.64  per  cent,  of  CbgOs  and  16.87  cent,  of  NagO. 


Calculated.  Found. 

7Na20 434  16.73  16.87 

6Cb205  1602  61.76  61.64 

31H2O 558  21.51  21.61 


2594  100.00  100.12 

The  clear  mother  liquors  from  the  recrystallization  of  this  salt  were 
placed  in  a threediter  platinum  dish,  the  latter  being  covered  with  a sheet 
of  filter  paper,  and  the  solution  was  allowed  to  evaporate  spontaneously. 


OBSERVATIONS  ON  COBUMBIUM. 


1651 

'1 

On  examining  the  dish  several  weeks  later,  a large  quantity  of  beautiful 
triclinic  crystals  was  found  to  have  separated  from  the  solution.  On 
analysis  they  proved  to  have  the  composition  Na2O.Cb2O5.7H2O.  A 
second  preparation,  made  in  the  same 
way,  gave  identical  results.  It  seems 
very  probable  that  Rose  obtained  this 
salt  in  an  impure  form  and  that  it  is  the 
one  to  which  Rammelsberg  assigned  the 
composition  Na2O.Cb2O5.9H2O,  a conclu- 
sion reached  from  a comparison  of  Rose’s 
results  given  on  page  1647  with  those 
which  follow. 

Analyses  of  powdered  samples  from  the 
two  preparations  gave: 

Calculated:  NagO,  13.63;  CbgOs,  58.68;  7H2O, 

27.69.  Found:  NajO,  13.77,  1386;  CbgOs, 

58.70,  58.73;  7H2O,  27.76,  27.80. 

Crystallography} — The  crystal  habit  of 
this  salt  is  shown  in  Fig.  4.  The  crystals 
were  about  2 mm.  in  length  and  fairly 
brilliant.  Their  faces,  however,  were 
more  or  less  striated  and  irregular,  giving 
multiple  or  indistinct  images.  Conse- 
quently the  results  obtained,  although  representing  the  means  of  the 
measurements  from  about  twenty  crystals,  can  only  be  considered  as  ap- 
proximately correct. 


Triclinic. — Axes,  a:  b:  c:  0.9559:  i 

.•0.8394.  a 

= 71°  20';  p = 105°  30'; 

r = 54°  7'. 

Measured. 

Measured. 

Calculated. 

ac. 

100  A 001  = * 53°  40' 

cm', 

, 001  A lio  = 89°  45' 

89°  55' 

be. 

010  A 001  = *127°  38' 

cp. 

001  A III  = 36°  52' 

36°  25' 

ab. 

100  A 010  = *137°  22' 

mp. 

no  A III  = 53°  23' 

53°  40' 

bm. 

'10 

0 

0 

* 

II 

0 

< 

0 

0 

ck, 

001  Aon  = 63°  34' 

' 63°  43' 

ex', 

001  A loi  = * 64°  40' 

bk. 

010  A on  = 64°  4' 

63°  55' 

Magnesium  Columbate,  MgO.Cb^O^.yH^O. — ^This  salt  was  obtained  as 
a white,  flocculent  precipitate  when  a solution  of  magnesium  chloride 
was  added  to  a solution  of  the  i ; i sodium  columbate.  It  was  washed 
by  decantation,  filtered  out  and  dried  on  a water  bath  for  several  hours. 

Analysis:  A sample  was  ignited  in  a platinum  crucible,  the  loss  in 
weight  representing  the  water.  The  ignited  material  was  then  fused 
with  potassium  bisulphate,  the  melt  treated  with  boiling  water  and  the 

^ Sincere  thanks  are  here  given  to  Professor  Amos  P.  Brown  and  to  Dr.  Charles 
Travis,  both  of  this  University,  for  invaluable  suggestions  and  assistance  in  connec- 
tion with  the  crystallographic  part  of  the  investigation. 


1652 


CIvARENCK  W.  BALKE  AND  EDGAR  E.  SMITH. 


columbium  oxide  filtered  out.  The  magnesium  was  determined  in  the 
filtrate  as  usual. 

Calculated:  MgO,  9.32;  CbaOg,  61.61;  7H2O,  29.07. 

Found:  MgO,  9.47;  CbaOj,  61.51;  7H2O,  29.17. 

Silver  Salts,  Ag^O .Cb20^.2H 2O . — When  a solution  of  silver  nitrate 
was  added  to  a solution  of  the  i ; i sodium  columbate,  a white  precipitate 

was  formed  which  had  a slight  yellow  color  when  dry.  It  darkened  slowly 

on  exposure  to  sunlight.  In  the  analysis  of  this  salt  the  water  content 
was  determined  directly. 

Calculated:  AgjO,  43-36;  CbjOe,  49-9i;  2H2O,  6.73. 

Found:  AgjO,  43-05;  CbjOs,  49-53;  2H2O,  6.61. 

Copper  Salt,  Cu0.Cb20^.3)4H20. — ^This  salt  was  obtained  as  a green 
precipitate  on  adding  a solution  of  copper  sulphate  to  a solution  of  the 
I :i  sodium  columbate.  On  ignition  it  became  deep  brown  in  color. 

Calculated:  CuO,  19.43;  CbgOs,  65.19;  3-5H2O,  15.38. 

Found:  CuO,  19.37;  CbjOs,  65.23;  3.5H2O,  14.97. 

Aluminium  Columbate,  Al20^.sCb20^.i2H20. — This  salt  appeared  as 
a white  precipitate  when  a solution  of  alum  was  added  to  a solution  of 
sodium  columbate. 

Calculated:  AI2O3,  9.12;  3Cba05,  71.58;  12H2O,  19.30. 

Found:  AljOj,  9.52;  3Cb206,  71-51;  12H2O,  18.97. 

Cadmium  Salt,  Cd0.Cb20^.3%H20. — ^This  salt  was  obtained  as  a 
yellowish  white  precipitate  when  a cadmium  salt  solution  was  added  to 
a solution  of  the  i :i  sodium  columbate. 

Calculated:  CdO,  28.01;  CbgOs,  58.25;  3.5H2O,  13.74. 

Found:  CdO,  28.06  (diff.);  CbaOg,  58.03;  3.5H2O,  13.91. 

4:3  Columbates. 

Potassium  Salt,  4K20.3Cb20^.i  6H2O. — Marignac  prepared  this  salt 
by  fusing  columbic  oxide  with  2-3  parts  of  potassium  carbonate.  It 
crystallizes  in  large  well  defined  monoclinic  crystals,  very  soluble  in  water. 
This  salt  was  made  a number  of  times  and  in  one  instance  40  grams  of 
columbic  oxide  were  fused  with  70  grams  of  potassium  carbonate,  and 
the  fused  mass  heated  with  a blast  lamp  as  long  as  any  carbon  dioxide 
was  expelled.  The  melt  was  completely  soluble  in  water  and  the  solution, 
on  standing,  deposited  crystals  several  centimeters  in  length.  Crystals 
from  two  different  preparations  were  analyzed  with  the  following  results: 

Calculated:  4K2O,  25.72;  3Cb205,  54-64;  16H2O,  19.64. 

Found:  4K2O,  25.90,  26.11;  3Cb20s,  54-22,  54-49;  16H2O,  i9-77»  i9-39- 

Marignac  found:  K2O,  25.32;  Cb20s,  53.88;  H2O,  19.12. 

Crystallography. — ^The  crystal  habit  of  this  salt  is  shown  in  Fig.  5. 
The  pyramid  faces  d and  d'  were  observed  on  only  a few  of  the  crystals 
which  were  examined.  It  was  not  difficult  to  obtain  crystals  of  this 


OBSERVATIONS  ON  COEUMBIUM.  1 653 

salt  giving  good  reflections  of  the  signal  when  measured  with  the  goni- 
ometer. ^ I 

Monoclinic. — Axes,  k:  b:  c = 0.7120:  i:  0.5547.  ^ = 84°  19'. 


Measured. 

Calculated. 

Marigoac  found. 

mm'" 

, no  A ilo  = *70°  38' 

0 

0 

cm. 

001  A no  = *85°  22' 

85°  30' 

cn. 

001  A In  = *45°  53' 

cn". 

001  A III  = 134°  7' 

134°  7' 

134°  6' 

cz. 

001  A 021  = 47°  51' 

47°  50' 

47°  50' 

cd. 

001  A III  = 41°  20' 

41°  27i' 

nz. 

In  A 021  = 39°  8' 

39°  6^ 

mz, 

no  A 021  = 68°  6' 

68°  li' 

m'z. 

Iio  A 021  = 61°  8' 

61°  SY 

nn' 

In  A III  = 49°  13' 

49°  13' 

bn, 

010  A In  = 65°  20' 

65°23i' 

65°  18' 

Rubidium 

Salt,  4Rb^0.3Cb20^.i4Hfi.- 

— In  the 

first  preparation 

this  salt  15  grams  of  columbium  oxide  were 
fused  with  20  grams  of  rubidium  carbonate. 

On  taking  up  the  melt  with  water  a mass  of 
fine  needles  remained  insoluble.  These  proved 
to  be  an  acid  rubidium  columbate.  On  con- 
centrating the  filtrate  from  these  needles, 
beautiful  monoclinic  crystals  separated  hav- 
ing the  composition  indicated  above.  This 
salt  was  very  soluble  in  water  and  it  slowly 
lost  water  on  exposure  to  the  air.  On  igni- 
tion in  a platinum  crucible  the  crystals  lost 
their  water  content  and  finally  fused  to  a 
transparent  liquid,  which  solidified  to  a crys- 
talline mass  on  cooling.  On  treating  this  mass 
with  water  a part  of  the  rubidium  oxide  dissolved,  leaving  a mass  of 
pearly  needles  which  were  probably  identical  with  those  mentioned  above. 

Calculated:  4Rb20,  41 -53 1 sCbgOs,  44-48;  14H2O,  i3-99- 

Found:  4Rb20,  42.20;  3Cb20s,  44.26;  14H2O,  14.10. 

In  a second  preparation,  10  grams  of  columbium  oxide  were  fused  with 
25  grams  of  rubidium  carbonate,  and  in  this  case  the  melt  was  completely 
soluble  in  water. 

Found:  4Rb20,  41.66;  3Cb206,  44.63;  14H2O,  13.82. 

Crystallography. — ^This  salt  is  one  of  four  isomorphous  salts  obtained 
during  the  present  investigation.  They  are: 

4Rb20.3Cb20s.  14H2O  4Cs20.3Cb205. 14H2O 

4Rb20.3Ta205.i4H20  4Cs20.3Ta205.i4H20 

The  angular  measurements  of  the  crystals  of  these  salts  were  identical 
within  the  limits  of  error  made  in  the  measurements.  It  was  difficult 


1654  ClyARENCE  W.  BAIvK^  AND  EDGAR  E.  SMITH. 

to  get  good  measurements  in  the  case  of  the  cesium  salts,  but  very  good 
results  were  obtained  with  the  rubidium  salts.  Many  excellent  crystals 
were  obtained,  some  of  them  having  a diameter  of  15  mm.  or  more,  but 
on  exposure  to  the  air  they  gradually  became  moist  and  then  dull,  making 
them  unfit  for  further  measurement  with  the  goniometer.  The  crystal 
habit  is  shown  in  Fig.  6. 

The  measurements  obtained  from  crystals  of  the  rubidium  columbate 
are  as  follows: 

. . I 

Monoclinic. — Axes,  ^ : b : c = 0.8815  : i : 1.0491.  ^ = 84°  7'. 


Measured, 

Calculated. 

dd',  III  A III  = *65°  13' 

dn,  III  A In  = *78°  55' 

nn'.  III  A Til  = *70°  36' 

dn".  III  A Hi  = 64°  27' 

64°  30' 

cd,  001  A III  = 54°  29' 

54'’  35' 

ad,  100  A III  = 48^13' 

48°  7' 

ac,  100  A 001  = 84°  10' 

0 

00 

Cesium  Salt,  4.Cs^0.3Cb^0^.i4H20. — For  the  preparation  of  this  salt 
10  grams  of  columbium  oxide  were  fused  with  30  grams  of  cesium  car- 
bonate. All  of  the  cesium  salts  used  in  the 
present  investigation  were  purified  by  recrys- 
tallizing the  salt  CsCl2ld  The  melt  was  com- 
pletely soluble  in  water  and  from  the  solution 
monoclinic  crystals  separated  which  were  iso- 
morphous  with  the  preceding  salt.  When  ig- 
nited this  salt  behaved  like  the  corresponding 
rubidium  salt.  On  treating  the  fused  salt 
with  water  a small  quantity  of  fine  pearly 
needles  remained  insoluble;  they  were  prob- 
ably  an  acid  cesium  columbate  corresponding 
to  the  acid  rubidium  columbate  which  was  mentioned  above.  This  salt 
was  not  obtained  in  quantities  large  enough  to  admit  of  analysis. 

Calculated:  4CS2O,  51-72;  sCbgOs,  36.73;  14H2O,  11.55. 

Found:  4CS2O,  51.42;  sCbjOj,  36.95;  14H2O,  11.88. 

7:6  Columbates. 

Potassium  Salt,  'jK^0.6Ch.JD^.2yH^0. — By  recrystallizing  the  4.3  po- 
tassium columbate  from  water,  Marignac  obtained  a salt  to  which  he 
assigned  the  composition  8K20.7Cb205.32H20.  The  result  of  his  analyses, 
however,  are  not  far  from  the  requirements  of  the  7 : 6 ratio  obtained  in 
the  present  investigation,  and  in  the  light  of  our  results,  it  seems  quite 
probable  that  the  salt  which  he  had  in  hand  was  of  the  latter  type. 

This  salt  was  obtained  by  adding  alcohol  to  a solution  of  the  4:3  salt. 

^ Wells,  Amer.  Jour.  Sci.,  43,  17  (1892). 


OBSERVATIONS  ON  COBUMBIUM. 


1655 


It  was  precipitated  by  this  treatment,  dissolved  in  water  and  again 
precipitated  by  alcohol,  filtered  out  by  suction  and  finally  washed  with 
alcohol  and  ether.  Analysis  I. 

An  aqueous  solution  of  this  precipitated  salt  deposited  crystals  having 
the  same  form  as  those  obtained  by  Marignac.  A sample  was  ground  to 
a powder  and  analyzed.  Analysis  II. 

For  the  sake  of  comparison  the  mean  of  Marignac’s  analyses  and  the 
requirements  for  an  8:7  ratio  are  included  in  the  following  table. 

Found. 

Calculated  for  Calculated  for 

7K20.6Cb205.27H20.  I.  II.  Marignac.  8K20.7Cb..>05.32H20. 


Per  cent.  Per  cent.  Per  cent.  Per  cent.  Per  cent. 

7K2O 660  24.02  24.10  24.15  23.47  23.57 

6Cb206 1602  58.30  58.21  58.31  58.35  58.42 

27H2O 486  17.68  17-83  17-61  17-35  18.01 


2748  100.00  100.14  100.07  99- 17  100.00 

Lithium  Salt,  yLi20.6Ch20^.26H^0. — A solution  of  lithium  nitrate, 
containing  sufficient  lithium  carbonate  to  render  it  slightly  alkaline,  was 
added  to  a strong  solution  of  the  7 :6  potassium  columbate.  Upon  warm- 
ing the  solution  a crystalline  salt  separated  which  was  filtered  out,  washed 
with  cold  water  and  dried  on  a porous  plate. 

Calculated:  7Li20,  9.21;  dCbgOs,  70.26;  26H2O,  20.53. 

Found:  7Li20,  9.22;  dCbgOs,  70.28;  26H2O,  20,44. 

Cesium  Salt,  yCs^O.dCh^O^.joH^O. — On  adding  alcohol  to  an  aqueous 
solution  of  the  4 : 3 cesium  columbate,  a heavy  oily-appearing  liquid  sepa- 
rated on  the  bottom  of  the  beaker.  On  further  washing  with  alcohol 
this  solidified  to  a crystalline  mass.  This  was  filtered  out,  washed  with 
alcohol  and  dried  between  folds  of  filter  paper.  On  ignition  it  behaved 
like  the  4 : 3 salt. 

Calculated:  7CS2O,  47.96;  6Cb205,  38.92;  30H2O,  13.12. 

Found:  7CS2O,  47-931  6Cb206,  38.71;  30H2O,  13.14.. 

5. *4  Rubidium  Columbate,  jRb20.4Cb20^.9j4H20. — This  salt,  con- 
sisting of  fine  silky  needles,  was  obtained  when  columbium  oxide  was 
fused  with  a limited  amount  of  rubidium  carbonate,  or  when  the  4 : 3 
rubidium  columbate  was  ignited  to  the  point  of  fusion.  It  was  very 
difficult  to  obtain  a pure  sample  for  analysis,  but  the  results  obtained 
agree  fairly  well  with  those  required  by  the  formula  given  above. 

Analysis:  The  water  was  determined  as  loss  on  ignition.  The  ignited 
sample  was  then  dissolved  in  hydrofluoric  acid,  and  the  analysis  com- 
pleted as  in  the  case  of  the  double  fluorides. 

Calculated:  3Rb20,  31-17;  4Cb20s,  59-33;  9-5H2O,  9.50. 

Found:  3^620,  30.66;  4Cb205,  60.33;  9-5H2O,  9.52. 


1656 


CLARKNCK  W.  BAlvKE  AND  EDGAR  R.  SMITH. 


Percolumbates. 

The  following  percolumbates  have  been  described  by  Melikoff  and 
Pissarjewsky  d 

HCbO^  + nH^O  K.Chfi,,  + 3H2O 

KCbO^  + nUfi 

The  free  percolumbic  acid  was  obtained  by  heating  columbium  hy- 
droxide with  a 30  per  cent,  solution  of  hydrogen  peroxide,  or  by  adding 
dilute  sulphuric  acid  to  a solution  of  the  potassium  percolumbate,  dialyz- 
ing out  the  excess  of  sulphuric  acid  and  potassium  sulphate,  and  then 
evaporating  the  clear  yellow  solution  to  dryness  on  a water  bath.  It 
is  described  as  being  a yellow  amorphous  powder,  insoluble  in  water. 

Hall  and  Smith^  obtained  a yellow  precipitate  on  adding  a solution  of 
hydrogen  peroxide  to  a hydrochloric  acid  solution  of  columbium  hydroxide. 
This  proved  to  be  a hydrated  percolumbic  acid  to  which  they  assigned 
the  composition  Cb(OH)g  or  Cb205H202.5H20. 

During  the  present  investigation  the  following  percolumbates  were 
obtained : 


I. 

NagCbOg 

MgNaCb0g.8H20 

CaNaCb0g.4H20 

KjChOg 

MgKCbOg.yHaO 

CaKCb0g.4H20 

RbjCbOg 

MgRbCbOg.TiH^O 

CSgCbOg 

MgCsCb0g.8H20 

The  compounds  given  under  I were  produced  by  adding  hydrogen 
peroxide  in  excess  to  solutions  containing  the  corresponding  columbates 
and  an  excess  of  the  proper  alkali  carbonate  or  hydroxide.  They  were 
most  easily  obtained  from  such  solutions  by  the  addition  of  an  equal 
volume  of  alcohol,  the  percolumbate  separating  as  a white  powder,  which 
was  filtered  by  suction  and  finally  washed  with  alcohol  and  ether.  They 
were  perfectly  stable  in  the  air  and  dissolved  in  warm  water  without 
decomposition.  However,  oxygen  escaped  when  their  solutions  were 
heated  to  the  boiling  temperature.  On  exposure  to  the  light,  the  rubidium 
and  cesium  percolumbates  darkened  perceptibly.  This  was  particularly 
true  in  the  case  of  the  cesium  salt. 

Analysis:  One  half  of  the  oxygen  present  in  the  percolumbates  is 
active  and  is  expelled  on  ignition.  The  ignition  was  made  in  a hard  glass 
tube  containing  a plug  of  asbestos  to  prevent  mechanical  loss  of  ma- 
terial. The  loss  in  weight  represented  the  active  oxygen.  A second 
sample  was  dissolved  in  water  and  treated  with  dilute  sulphuric  acid.  . 
No  precipitate  was  produced  at  first,  but  on  boiling  the  solution  a part 
of  the  active  oxygen  was  expelled  and  a yellow  precipitate  separated, 
probably  |a  hydrated ’peroxide  of  columbium.  This  was  filtered  out, 

^ Z.  anorg.  Chem.,  20,  340  (1899). 

2 This  Journal,  27,  1369  (1905). 


OBSERVATIONS  ON  COEUMBIUM. 


1657 


washed,  ignited  and  weighed  as  columbic  oxide,  Cb205.  The  filtrate 
was  evaporated  to  dryness  and  the  alkali  determined  as  sulphate.  The 
latter  usually  contained  a small  amount  of  columbium  so  that  it  was 
generally  necessary  to  dissolve  the  ignited  sulphate  in  a small  amount 
of  water,  filter  out  the  columbium  hydroxide  and  finally  reweigh  the 
alkali  sulphate. 

Sodium  Percolumbate,  Na^CbO^. — ^This  salt  was  more  difficult  to  pre- 
pare than  the  corresponding  percolumbate  of  the  other  alkali  metals, 
because  of  the  comparative  insolubility  of  the  sodium  columbate  used 
as  the  starting-out  material.  The  following  procedure  was  finally 
adopted  for  its  preparation : sodium  columbate  (the  7 ; 6 salt,  one  part) 
was  dissolved  in  as  little  boiling  water  as  possible,  the  solution  was  added 
to  a warm  solution  of  hydrogen  peroxide  and  sodium  hydroxide  (75-100 
parts  of  a 3 per  cent,  solution  of  hydrogen  peroxide  and  2 parts  of 
sodium  hydroxide),  the  solution  was  filtered  by  suction,  and  an  equal 
volume  of  alcohol  was  then  added.  The  percolumbate,  precipitated  by 
this  treatment,  was  filtered  out  by  suction,  dissolved  in  warm  water  and 
again  treated  with  a 3 per  cent,  solution  of  hydrogen  peroxide  contain- 
ing a small  amount  of  sodium  hydroxide.  The  sodium  percolumbate 
was  again  precipitated  from  the  solution  by  the  addition  of  an  equal 
volume  of  alcohol,  filtered  by  suction  and  finally  washed  with  alcohol 
and  ether. 

Calculated:  i.5Na^O,  32.01;  o.sCbgOs,  45-96;  4O,  22.03. 

Found:  i-sNajO,  31-88;  o.sCbA.  45-75;  4O,  21.85. 

Potassium  Percolumbate,  K^CbO^. — A portion  of  this  salt,  obtained  by 
precipitation  with  alcohol  as  previously  described,  gave  the  following 
results  on  analysis: 

Calculated:  1.5K2O,  4^-74;  o-5Cb20s,  39.38;  4O,  18.88. 

Found:  1.5K2O,  40.90;  o.5Cb20s,  39-35;  4O,  18.96. 

It  was  found  possible  to  prepare  this  salt  without  the  use  of  alcohol. 
A warm  solution  of  10  grams  of  the  4 : 3 potassium  columbate  and  40  grams 
of  potassium  hydroxide,  free  from  sodium,  were  added  to  an  excess  of  a 3 
per  cent,  hydrogen  peroxide  solution.  A large 
quantity  of  the  potassium  percolumbate  sepa- 
rated immediately  in  the  form  of  small  but 
well  defined  tetragonal  crystals  showing  the 
faces  of  the  prism  and  pyramid  of  reverse 
orders.  Measured  with  the  microscope,  the 
angle  between  the  intersection  of  the  faces  a 
and  c (Fig.  7)  and  the  intersection  of  the  faces 
c and  p was  found  to  be  45°,  and  the  upper 
angle  between  the  vertical  edge  of  aa  (100  A 010)  ^^8-  7- 


1658 


CI.ARKNCE;  W.  BALKR  AND  EDGAR  R.  SMITH. 


and  the  intersection  of  the  faces  a (100)  and  p (iii)  was  found  to  be 
49°  5o^  giving  0.844  as  the  value  of  c. 

These  crystals  gave  the  following  results  on  analysis: 

Found:  1.5K2O,  41.82;  o.sCbgOs,  39-45;  40,  18.91.'’ 

This  salt  was  prepared  a number  of  times  with  identical  results,  and 
inasmuch  as  perfectly  analogous  salts  were  obtained  with  the  other 
alkali  metals,  the  work  of  Melikoff  and  Pissarjewsky  on  the  potassium 
percolumbate,  to  which  they  assigned  the  composition  K4Cb20ii.3H20, 
was  repeated  following  their  directions  as  closely  as  possible.  They 
made  their  salt  as  follows:  Columbic  oxide  was  fused  with  potassium 
hydroxide  (iCb205  to  8K0H)  in  a silver  crucible.  The  fusion  was  dis- 
solved in  a small  amount  of  water  and  after  the  addition  of  a small  quantity 
of  hydrogen  peroxide,  the  solution  was  warmed  for  a short  time  on  a 
water  bath.  Any  black  precipitate  (silver)  which  separated  was  filtered 
out,  hydrogen  peroxide  (iCb205  to  9-10H2O2)  was  added  to  the  solution 
and  this  was  followed  by  an  equal  volume  of  alcohol,  whereupon  a floccu- 
lent  white  precipitate  separated,  which  was  washed  with  alcohol  and 
ether  and  dried  on  a porous  plate.  This  precipitate  was  dissolved  in  water, 
hydrogen  peroxide  (iCb205  to  3-4H2O2)  and  potassium  hydroxide  (iCb205 
to  1/2KOH)  were  added  to  the  solution  and  the  salt  was  again  precipi- 
tated by  the  addition  of  alcohol  (i-i^  vol.).  The  product  was  a white 
crystalline  precipitate  which  was  washed  with  alcohol  and  ether. 

This  procedure  was  carried  out  a number  of  times,  but  the  salt  de- 
scribed by  Melikoff  and  Pissarjewsky  was  not  obtained.  In  nearly 
every  case  the  salt  KgCbOg  appeared,  and  it  seems  very  probable  that 
the  latter  salt  will  always  be  formed  when  the  solution  contains  a suf- 
ficient amount  of  hydrogen  peroxide  to  yield  the  requisite  quantity  of 
oxygen.  The  potassium  hydroxide  used  in  the  preparation  of  this  salt 
must  be  free  from  sodium,  for  otherwise  the  7:6  sodium  columbate  will 
result  from  the  fusion  of  the  columbic  oxide  with  the  hydroxide  and  re- 
main insoluble  in  the  alkaline  solution  when  the  melt  is  treated  with  water. 

Rubidium  Percolumbate,  RbfihO^. — An  excess  of  hydrogen  peroxide 
was  added  to  a solution  containing  4 grams  of  the  4 : 3 rubidium  columbate 
and  10  grams  of  rubidium  carbonate.  On  adding  an  equal  volume  of 
alcohol  a white  crystalline  powder  was  precipitated  from  the  solution. 
This  was  filtered  out,  washed  with  alcohol  and  ether  and  allowed  to  dry 
in  the  air. 

Calculated:  i.sRbjO,  58.68;  o.sCbaOg,  27.93;  4O,  I3-39- 
Found:  i.5Rb20,  58.34;  o.5Cb20s,  27.66;  4O,  13.26. 

Cesium  Percolumbate,  CsfibO^. — This  salt  was  prepared  in  the  same 
manner  as  the  rubidium  salt,  and  gave  the  following  analysis; 

Calculated:  1.5CS2O,  68.17;  o.5Cb205,  21.52;  4O,  10.31. 

Found:  1.5CS2O,  67.91;  o.5Cb206,  21.46;  4O,  10.31. 


OBSEJRVATIONS  ON  COBUMBIUM. 


1659 

The  substances,  whose  formulas  are  given  under  II,  are  all  crystalline  salts 
obtained  when  solutions  of  magnesium  or  calcium  chlorides  are  added 
to  solutions  of  the  previously  described  percolumbates.  The  magnesium 
salts  are  soluble  in  water  without  decomposition,  but  they  are  less  soluble 
than  the  corresponding  percolumbates,  while  the  calcium  salts  are  diffi- 
cultly soluble  in  water. 

For  the  preparation  of  these  salts  the  percolumbate  was  dissolved  in 
as  little  warm  (50°)  water  as  possible  and  to  this  solution  there  was  added 
a strong  neutral  or  slightly  alkaline  solution  of  the  alkaline-earth  chloride. 
The  double  percolumbate  crystallized  from  the  solution,  usually  in  the 
form  of  very  fine  silky  needles,  which  were  filtered  out  and  washed  with 
alcohol  and  ether.  It  was  sometimes  found  desirable  to  add  a small 
amount  of  alcohol  to  the  solution  to  render  the  separation  of  the  salt 
more  complete.  This  was  particularly  true  in  the  case  of  the  rubidium 
and  cesium  salts. 

Analysis;  For  the  determination  of  the  active  oxygen  and  water  a 
sample  was  weighed  out  in  a short,  hard  glass  tube  closed  at  one  end. 
A plug  of  asbestos  was  placed  in  the  tube  above  the  salt  to  prevent  loss 
by  decrepitation  and  after  being  weighed  the  tube  was  connected  to  the 
top  of  a Hempel  gas  burette  by  means  of  a short  piece  of  rubber  tubing. 
On  gently  heating  the  tube,  water  was  expelled  at  first,  and  then  at  a high 
temperature  oxygen  was  evolved,  and  from  its  corrected  volume  the 
amount  of  active  oxygen  in  the  salt  was  easily  calculated.  The  tube  was 
reweighed  and  its  loss  in  weight  gave  the  sum  of  the  active  oxygen  and 
water,  the  latter  being  finally  determined  by  difference. 

To  complete  the  analysis  of  the  magnesium  salts,  a sample  was  dis- 
solved in  water  and  treated  with  a few  drops  of  dilute  sulphuric  acid. 
No  precipitate  was  formed  at  first,  but  a yellow  color  was  produced. 
On  adding  a small  amount  of  alcohol  and  boiling,  oxygen  was  expelled 
and  a yellow  hydrated  percolumbic  acid  was  precipitated.  This  was 
filtered  out,  the  filtrate  was  evaporated  to  a small  bulk  and  heated  until 
the  vapors  of  sulphuric  acid  escaped.  On  taking  up  the  residue  in  water, 
an  additional  quantity  of  columbium  hydroxide  was  obtained.  This 
was  filtered  out  and  the  magnesium  was  determined  in  the  filtrate  as 
usual.  The  alkali  oxide  was  determined  by  difference.  In  one  or  two 
cases  the  ignited  salt  was  fused  with  potassium  bisulphate,  the  mass 
was  treated  with  water  and  the  columbium  hydroxide  was  filtered  out 
and  weighed  as  usual.  The  magnesium  was  determined  in  the  filtrate. 

In  the  case  of  the  calcium  salts  the  precipitation  of  the  columbium 
hydroxide  was  made  with  nitric  acid,  but  in  other  respects  the  method 
of  analysis  was  the  same  as  that  described  above. 

Magnesium  Sodium  Percolumbate,  MgNaCbO^.SH^O. — In  the  prepara- 
tion of  this  salt  a small  amount  of  a flocculent  precipitate  was  produced 


i66o 


CIvARHNCH  W.  BAIvKB  AND  BDGAR  R.  SMITH. 


when  a solution  of  magnesium  chloride  was  added  to  a solution  of  sodium 
percolumbate.  This  was  filtered  out  as  rapidly  as  possible  and  the  above 
salt  separated  from  the  filtrate. 

Calculated:  MgO,  9.78;  o.sNagO,  7.51;  o.sCbaOs,  32.33;  4O,  15.50;  SHgO,  34.88. 

Found:  MgO,  9.84;  o.5Na.p,  7.40  (diff.);  o.5Cb205,  32.23;  4O,  14.89;  8H2O,  35-64- 

Magnesium  Potassium  Percolumbate,  MgKCbO^.yHfi. — Analysis: 

Calculated:  MgO,  9.83;o.5K20,  11.46;  o.5Cb205,  32.48;  4O,  15.57;  7H2O,  30.66. 

Found:  MgO,  9.88;  0.5K2O,  11.56  (diff.);  o.5Cb205,  32.46;  4O,  15.48;  7H2O,  30.62. 

Magnesium  Rubidium  Percolumbate,  MgRbCb0^.7}^H20. — This  salt 
gave  the  following  results  on  analysis: 

Calculated:  MgO,  8.66;  o.5Rb20,  20.05;  0.506305,  28.62;  4O,  13.72;  7.5H2O,  28.95. 

Found:  MgO,  9.21;  o.5Rb20,  19.26  (diff.);  0.506205,  28.81;  4O,  13.47;  7.5H2O,  29.25. 

Magnesium  Cesium  Percolumbate,  MgCsCbO^.SH^O. — This  salt  gave 
the  following  analytical  results: 

Calculated:  MgO,  7-73;  0.5CS2O,  26.96;  0.506305,  25.53;  40,  12.24;  8H2O,  27.54. 

Found:  MgO,  7.89;  0.5CS2O,  26.81  (diff.);  0.506305,  25.77;  4O,  12.18;  8H2O,  27.35. 

Calcium  Sodmm  Percolumbate,  CaNaCbOg.4H20. — Analysis: 

Calculated:  CaO,  15.71;  o.5Na20,  8.69;  0.506305,  37.45;  4O,  17.95;  4H2O,  20.20. 

Found:  CaO,  16.50;  o.5Na20,  8.16  (diff.);  0.506305,  37.31;  4O,  16.79;  4H2O,  21.24. 

Calcium  Potassium  Percolumbate,  CaKCb0^.4H20. — This  salt  gave 
the  following  analysis: 

Calculated:  CaO,  15.03;  0.5K2O,  12.64;  0.506305,  35.83;  4O,  17.18;  4H2O,  19.32. 

Found:  CaO,  15.49;  0.5K2O,  13.03  (diff.);  0.506305,  35.41;  40,  16.74;  4H2O,  19.33. 

Double  Fluorides  of  Columbium. 

H Rose^  studied  certain  double  fluorides  of  columbium  with  sodium 
and  potassium,  but  his  results  are  of  little  present  value,  due  probably 
to  the  impurity  of  his  material. 

In  addition  to  the  sodium  and  potassium  salts,  which  will  be  mentioned 
later,  Marignac  described  the  following  double  fluorides  of  columbium:^ 
2NH4F.CbOF3  2NH4F.CbF5  + NH4F.CbOF3 

3NH4F.CbOF3  ZnF2.CbOF3  + bH^O 

5NH4F.3CbOF3.H3O  CuF2.CbOF3  + 4H2O 

NH4F.CbOF3 

Santesson^  obtained  a salt  to  which  he  assigned  the  composition 
Zn5H5F3oCb3  + 28H2O  by  evaporating  a solution  of  zinc  carbonate  and 
columbic  acid  in  concentrated  hydrofluoric  acid.  It  was  insoluble  in 
cold  water  and  decomposed  by  hot  water.  Perfectly  analogous  salts 
of  cadmium,  manganese,  cobalt  and  nickel  were  obtained.  The  follow- 
ing were  also  prepared  and  are  described  as  crystalline  substances: 

^ Pogg.  Ann.,  104,  581,  1858. 

^ Bibl.  Univ.  Archives,  23,  249  (1865). 

2 Bull.  soc.  chim.  [2],  24,  52;  J.  B.,  1875,  218. 


OBSERVATIONS  ON  COLUMBIUM. 


l66l 


Ni3H4p2oCb2  + 19H2O  Cu^H.FioCb  + iqH^O 

Fe3H4p3oCb3  + 19H3O  Hg^F^^Cb  + 8H3O. 

Kriiss  and  Nilson^  assigned  the  composition  2KF.3Cb02F  to  the  white 
precipitate  obtained  on  boiling  a solution  of  the  ordinary  potassium 
fluoxycolumbate. 

Piccini^  obtained  a potassium  fluoxypercolumbate  having  the  com- 
position K2Cb02F5.H20.  This  salt  has  been  further  studied  by  Hall 
and  Smith. 

Pennington®  described  two  double  fluorides  of  columbium  to  which 
were  assigned  the  formulas  2RbF.CbF5  and  yCsF.CbFg. 

Sodium  Salts. — In  his  study  of  the  double  fluorides  of  columbium, 
Marignac  states  that  he  obtained  the  sodium  salts  in  the  form  of  crystal- 
line crusts  having  a more  or  less  indefinite  composition.  No  analyses 
are  given,  but  he  claims  that  his  results  point  to  the  existence  of  at  least 
two  fluoxycolumbates  of  sodium  having  the  composition  indicated  by 
the  formulas  2NaF.CbOF3.2H2O  and  NaF.CbOF3.H2O. 

We  were  unable  to  confirm  conclusively  the  existence  of  these  two 
salts,  but  our  results  indicate  the  probable  existence  of  a number  of  double 
fluorides  of  columbium  with  sodium.  Inasmuch  as  they  crystallize 
very  poorly,  we  were  able  to  obtain  but  one  of  them  sufficiently  pure 
to  deduce  a formula. 

jNaF.CbOF^. — Thirty  grams  of  columbic  oxide  and  24  of  sodium 
carbonate  were  dissolved  in  hydrofluoric  acid,  and  the  solution  was  evapo- 
rated to  dryness  several  times  to  expel  the  excess  of  acid.  The  salt  was 

then  dissolved  in  hot  water  and  allowed  to  crystallize.  A crystalline 

crust  which  separated  from  the  solution  was  removed  and  crystallized 
from  water.  The  salt,  which  again  separated  in  crystalline  crusts,  had 
the  composition  indicated  above,  as  shown  by  the  following  analyses: 

Calculated:  3Na,  23.59;  Cb,  31.97;  6F,  38.97. 

Found:  3Na,  23.57,  23.62;  Cb,  32.15,  32.14;  6F,  38.88, 

sNaF.Ch02F^.H.p. — Hydrogen  peroxide  and  a few  drops  of  hydro- 
fluoric acid  were  added  to  a solution  of  the  above  salt,  and  the  yellow 
solution  thus  obtained  was  allowed  to  evaporate  spontaneously.  On 
long  standing,  beautiful,  well  defined  crystals  separated.  They  were 
of  a pale  yellow  color  and  when  removed  from  the  solution  they  were 
perfectly  transparent,  but  gradually  became  dull  and  opaque  on  con- 
tinued exposure  to  the  air. 

Calculated:  3Na,  21.13;  Cb,  28.64;  6F,  34.92;  O (active),  4.90;  HgO,  5.51. 

Found:  3Na,  21.05;  Cb,  28.27;  6F,  35.64;  O (active),  4.66;  H^O,  5.20. 

^ Ber.,  20,  1689  (1887). 

^ Z.  anorg.  Chem.,  2,  21  (1892). 

8 This  Journal,  18,  38  (1896). 


i662 


CI^ARENCE  W.  BAhKH  AND  EDGAR  E.  SMITH. 


Potassium  Salts. — Marignac  described  and  analyzed  the  following 
double  fluorides  of  potassium  and  columbium: 


The  first  of  these  salts  is  the  one  ordinarily  obtained  and  is  formed 
when  any  of  the  other  salts  are  recrystallized  from  water.  The  last  salt 
in  the  series  is  produced  when  the  other  salts  are  recrystallized  from 
strong  hydrofluoric  acid.  Its  use  in  the  purification  of  columbium  has 
already  been  described.  Because  of  the  large  number  and  the  com- 
plexity of  some  of  these  salts  described  by  Marignac,  it  was  thought  worth 
while  to  prepare  them  again  with  the  pure  material  at  hand.  Our  results 
confirm  the  existence  of  all  of  them. 

sKF.CbOF^. — This  salt,  which  Marignac  designated  the  cubic  fluoxy- 
columbate  of  potassium,  crystallizes  from  solutions  containing  an  ex- 
cess of  potassium  fluoride.  In  describing  the  crystalline  form  of  this 
salt,  Marignac  said:  “These  crystals  have  exactly  the  appearance  of 
cubes  without  any  modification.  But  optical  examination  proves  that 
they  belong  neither  to  the  cubical  system  nor  to  that  of  the  square  pris- 
matic. Besides,  their  angles  are  not  exactly  right  angles,  the  determi- 
nations varying  between  90°  and  90°  30',  and  accordingly  it  has  been 
impossible  for  me  to  determine  their  crystalline  system.”  However, 
H.  Baker!  obtained  crystals  of  this  salt  which  were  perfectly  inactive, 
so  that  they  probably  belong  to  the  isometric  system,  and  are  isomorphous 
with  the  salts  3NH4F.CbOF3,  3NH4F.ZrF4  and  3KF.ZrF4. 

During  the  present  investigation  this  salt  was  prepared  by  concentra- 
ting a solution  containing  40  grams  of  the  salt  2KF.CbOF3.H2O,  and  30 
grams  of  potassium  fluoride.  The  salt  separated  from  the  solution  in 
the  form  of  small  brilliant  crystals,  which  had  every  appearance  of  being 
isometric  cubes;  however,  when  rotated  in  polarized  light,  the  edges, 
but  not  the  centers  of  many  of  these  crystals  possessed  a very  faint  double 
refraction. 

Calculated:  o.sCbgOs,  39- 15;  1.5K2SO4,  76.66;  6F,  33.43. 

Found:  o.sCbgOj,  38.97;  1.5K2SO4,  76.66;  6F,  33.14. 

Marignac  found  (mean):  o.5Cb205,  39.35;  1.5K2SO4,  76.12;  6F,  32.49. 

jKF.HF.CbOF^. — Marignac  called  this  salt  the  acicular  fluoxycolumbate 
of  potassium.  It  crystallizes  in  the  form  of  slender  needles  from  a solu- 
tion containing  an  excess  of  potassium  fluoride  and  hydrofluoric  acid. 
Crystals  of  this  and  the  following  two  salts  lose  their  luster  when  exposed 
to  the  air.  The  solution  from  which  we  obtained  the  best  crystals  was 
analyzed  and  found  to  contain  potassium  fluoride,  hydrofluoric  acid, 

! J.  Chem.  Soc.,  35,  760  (1879). 


2KF.CbOF3.H2O 

3KF.CbOF3 

3KF.HF.CbOF3 


5KF.3CbOF3.H2O 

4KF.3CbOF3.2H2O 

2KF.CbFs 


OBSKRVATIONS  ON  COLUMBIUM. 


1663 


and  columbium  fluoride  (CbFg)  in  the  proportions  1.8:1. 2:1.  According 
to  Marignac  this  salt  is  isomorphous  with  the  salt  3KF.HF.SnF4. 

Calculated:  • o.sCbgOs,  36.89;  1.5K2SO4,  7244;  ?F,  36.84;  H,  0.28. 

Found:  o.sCbjOs,  36-60;  1.5K2SO4,  72.01;  7F,  36.91;  H,  0.29. 

Marignac  found  (mean):  o.5Cb206,  36.90;  1.5K2SO4,  72.15;  7F,  37.80. 


Crystallography. — This  salt  crystallizes  in  needles  which  belong  to  the 
monoclinic  system.  The  crystals  were  not  large,  but  they  gave  fairly 
satisfactory  reflections.  The  crystal  habit  is  shown  in  Fig.  8.  The 
pinacoid  face  (001)  and  an  additional  face,  probably  a clinodome,  were 
also  observed,  but  they  were  too  small  for  measurement. 

I 


Monoclinic. — ^Axes,  b: 

c:  0.6304:  1 : 0.4888. 

/?  = 86°  4P. 

Measured. 

Calculated. 

Marignac  f< 

mm'" 

, no  A ilo  = *64°  22' 

64°  10' 

dd', 

III  A III  = *41°  8' 

0 

0 

nn', 

ill  A III  = 43°  12' 

43°  18' 

43°  26' 

dn, 

III  A In  = 69°  34' 

69°  43' 

69°  30' 

md, 

no  A III  = *45°  59' 

45°  52' 

mn', 

no  A Til  = 130°  53' 

130°  58' 

130°  54' 

^KF.jCbOF^.H.^0. — ^This  salt  crystallizes  from  solutions  containing 
columbium  fluoride  and  an  amount  of  potassium  fluoride  insufflcient  to 
form  the  2 : i potassium  fluoxycolumbate.  Its  crystals  are  prisms  with 
60°  angles,  but  they  probably  belong  to  the  monoclinic  system.  We  did 
not  succeed  in  obtaining  crystals  which  gave  satisfactory  measurements. 


Calculated:  i.sCbgOg,  49-55;  2.5K2SO4,  53-9i;  14F,  32.91;  H2O,  2.23. 

Found:  i.sCbgOj,  49-04;  2.5K2SO4,  53-19;  hF  33-6i;  H2O,  2.31. 

, Marignac  found:  i.5Cb205,  48.59;  25.K2SO4,  53-46;  14F,  31-84;  HgO,  2.00. 


4KF.JC6OF3.2//2O. — Marignac  called  this  salt  the  oblique  nonsym- 
metrical  fluoxycolumbate  of  potassium.  It  separates  from  solutions 
containing  potassium  fluoride  and  columbium  fluoride  when  the  latter 
is  present  in  great  excess,  iKFiqCbFg. 

Calculated:  i.5Cb205,  52.14;  2K2S04,  45-38;  13F,  32.16;  2H2O,  4.69 

Found:  i.5Cb205,  52.23;  2K2SO4,  45-29;  13F  31-70;  2H2O,  4.66. 

Marignac  found:  i.5Cb20s,  52.10;  2K2SO4,  45.30;  13F,  31.40;  2H2O,  4.70. 

Rubidium  Salts. — Miss  Pennington  states  that  the  salt  to  which  was 
assigned  the  formula  2RbF.CbF5  was  obtained  by  dissolving  0.5  gram 
of  columbium  oxide  in  hydrofluoric  acid  and  adding  the  calculated  quantity 
of  rubidium  fluoride,  evaporating  the  solution  to  dryness,  dissolving 
the  residue  in  water,  and  allowing  the  salt  to  crystallize  out  spontaneously. 
From  the  results  of  the  present  investigation  it  would  appear  that  the 
oxyfluoride,  2RbF.CbOF2,  is  formed  under  these  conditions.  No  salt 
having  the  composition  2RbF.CbF5  was  obtained. 

2RbF.CbOF^. — This  salt  crystallized  from  a solution  containing  rubid- 
ium fluoride  and  columbium  fluoride  in  the  required  proportions.  A 
portion  of  the  salt  was  recrystallized  from  water  and  analyzed. 


1664 


CIvARKNCK  W.  BALKK  AND  EDGAR  E.  SMITH. 


Calculated:  2Rb,  45.54;  Cb,  24.90;  5F,  25.30. 

Found:  2Rb,  45.54;  Cb,  24.94;  5F,  25.15. 

This  salt  was  recrystallized  from  an  excess  of  rubidium  fluoride,  and 

the  salt,  which  separated  in  the  form  of  thin 
pearly  plates,  gave  the  following  results  on 
analysis : 

Found:  2Rb,  45.66;  Cb,  24.83. 

RhF.ChF^. — The  preceding  salt  was  recrys- 
tallized three  times  from  35  per  cent,  hydro- 
fluoric acid.  By  this  treatment  it  was  con- 
verted into  a salt  consisting  of  small  needles 
which  gave  the  following  results  on  analysis: 

Calculated:  RbF,  35.67;  CbFg,  64.33. 

Found:  RbF,  35.72;  CbFj,  64.40. 

2RbF.Ch02F^.H20. — A quantity  of  the  salt 
2RbF.CbOF3  was  brought  into  solution  in 
dilute  hydrogen  peroxide  and  on  concentrating 
the  yellow  colored  liquid  which  resulted,  thin 
yellow  plates  separated.  These  were  recrys- 
tallized from  water  containing  a small  amount 
of  hydrofluoric  acid  and  hydrogen  peroxide. 
Pjg  g The  salt  had  the  same  appearance  as  the 

corresponding  potassium  salt  which  has  been 
studied  by  Piccini  and  by  Hall  and  Smith. 


m 


m 


Calculated:  2Rb,  41.76;  Cb,  22.83;  5F>  23.20;  O (active),  3.91;  HgO,  4.39. 

Found:  2Rb,  41.77;  Cb,  23.19;  5F,  23.16;  O (active),  3.95;  HjO,  4.36. 

2RbF.TaO2F2.H2O. — This  salt  was  prepared  from  the  salt  2RbF.TaFs 
by  the  same  method  as  that  used  for  the  preparation  of  the  preceding 
salt.  It  consisted  of  thin  white  leaflets  which  gave  the  following  analysis: 

Calculated:  2Rb,  34.27;  Ta,  36.67;  5F,  19.04;  O (active),  3.21;  HgO,  3.60. 

Found:  2Rb,  34.17;  Ta,  36.86;  5F,  19.25;  O (active),  3.13;  HgO,  3.76. 

Cesium  Salts,  2CsF.CbOF2. — This  salt  separated  from  solutions  con- 
taining cesium  fluoride  and  columbium  fluoride  in  widely  varying  pro- 
portions (iCbFg  to  4-ioCsF).  The  following  analyses  were  made  of  crops 
of  crystals  which  separated  from  solutions  containing  cesium  and  colum- 
bium fluorides  in  different  proportions.  No  salt  richer  in  cesium  fluoride 
was  obtained. 


Calculated:  2Cs,  56.54;  Cb,  19.87;  5F,  20.19. 

Found:  2Cs,  56.32,  56.24,  56.66;  Cb,  20.17,  19.82. 

Crystallography. — Hexagonal;  rhombohedral.  Axis  c — 0.949.  Crys- 
tals of  two  distinct  habits  were  observed:  (i)  simple  crystals  consisting 
of  the  prism  (loTo)  terminated  by  the  basal  pinacoid  (0001),  and  (2) 
twin  crystals  (Fig.  9),  twinning  plane  (loTi),  each  individual  consisting 


OBSERVATIONS  ON  COEUMBIUM. 


1665 


of  acute  plus  and  minus  rhombohedrons  {x  and  y),  symbols  undetermined, 
terminated  by  the  basal  pinacoid. 

The  axial  ratio  was  obtained  from  the  meas- 
ured angle  between  the  basal  pinacoids  of  the 
two  individuals  of  the  twin, 
c A c'  = 84°  45'. 

r A c,  (loTi)  A (0001)  = 47°  37K'- 
The  angle  x A c gave  discordant  measure- 
ments. X A c,  hoHl  A 0001  ~ 80°  to  90°. 

CsF.CbF^. — This  salt  was  obtained  in  the 
form  of  fine  needles  when  the  preceding 
salt  was  recrystallized  three  times  from  35 
per  cent,  hydrofluoric  acid.  It  gave  the  following  analysis: 

Calculated:  CsF,  44.64;  CbFj,  55.36. 

Found:  CsF,  44.31;  ChF^,  55.54. 


Thallium  Salt,  2TlF.ChOF^. — This  salt  separated  from  a solution 
containing  thallium  fluoride  and  columbium  fluoride,  in  the  required 

proportions,  in  the  form  of  trans- 
V parent,  colorless  crystals  belonging  to 

n the  orthorhombic  system.  It  is  easily 

^ soluble  in  water  and  may  be  recrys- 
~~y/  tallized,  in  which  case  it  separates  in 
/y  thin  plates  resembling  very  closely  the 

' ordinary  potassium  fluoxycolumbate. 

Analysis:  A sample  was  decom- 
posed with  sulphuric  acid,  and  the 
residue  was  treated  with  water.  It  was  found  to  be  impossible  to  wash 

the  columbic  oxide  free  from  thallous  ^ 

sulphate,  so  that  it  was  fused  with  ^ ^ 

potassium  bisulphate  and  again  di-  e 

gested  with  water.  The  thallium  was  l^ig*  n- 

determined  in  the  combined  filtrates  as  thallous  iodide.  A recrystallized 
sample  of  the  salt  consisting  of  thin  leaflets  gave  the  following  results: 


Fig.  10. 


Calculated:  2TI,  66.62;  Cb,  15.26;  5F,  15.51. 

Found:  2TI,  66.58;  Cb,  15.21;  5F,  15.62. 

A sample  of  the  original  plates  which  had  not  been  recrystallized  gave 
the  following  analysis : 

Found:  2TI,  66.07;  Cb,  15.36. 

Crystallography. — The  crystal  habit  of  this  salt  is  shown  in  Figs.  10 
and  II.  The  measurements  obtained  were  fairly  satisfactory. 


1 666 


CI.ARKNCB  W.  BALKE  AND  BDGAR  R.  SMITH. 


Orthorhombic. — Axes,  a : b : c = 0.4261  : i : 1.0129. 


Measured.  Calculated. 


cn, 

001  Aon 

= 45° 

22' 

ce, 

001  A loi 

= 67° 

n' 

en, 

loi  Aon 

= 74° 

10' 

74° 

iiK' 

ev, 

001  A 122 

= 72° 

13'K 

72° 

ev, 

loi  A 122 

= 38° 

4' 

38° 

8K' 

nv, 

on  A 122 

= 49° 

6' 

49° 

10' 

Tantalates,  4Rb.f).^Tafi^.i4H^0. — For  the  preparation  of  this  salt 
15  grams  of  tantalic  oxide  were  fused  with  25  grams  of  rubidium  car- 
bonate. The  melt  was  completely  solu- 
ble in  a small  quantity  of  warm  water, 
and  on  cooling  the  solution  there  sepa- 
rated beautiful  transparent  colorless  crys- 
tals which  were  isomorphous  with  the 
corresponding  rubidium  salt. 

Calculated:  4Rb20,  31*99;  sTagOs,  57*23; 

14H2O,  10.78. 

Found;  4Rb20,  31*38;  3Ta206,  57*5°;  14H2O, 
10.88. 

Crystallography. — As  previously  stated 
this  is  one  of  four  isomorphous  salts  ob- 
Fig*  12  tained  during  the  present  investigation. 

Nearly  all  of  the  crystals  had  the  form  shown  in  Fig.  12,  but  several  of  the 
crystals  which  had  a diameter  of  10-12  mm.  showed  the  additional  faces 
of  the  two  prisms  m and  u shown  in  Fig.  12. 


Monoclinic. — ^Axes,^:  b:  c:  = 0.8822:  i; 

Measured. 

1.05 10.  /?  = 84® 

Calculated. 

dd', 

in  A III 

= *65°  15' 

dn, 

III  A III 

= *78°  55' 

nn'. 

In  A III 

0 

0 

* 

11 

dn'". 

III  A III 

= 64°  23' 

64°  26' 

dm, 

III  A no 

= 30°  57' 

30°  56K' 

cd, 

001  A III 

= 54°  28' 

54°  34K' 

ad, 

100  A III 

= 48°  10' 

48°  5K' 

am. 

100  A no 

= 41°  13' 

41°  16' 

au, 

100  V 210 

= 23°  30' 

23°  41' 

4Cs2O.3Ta.2P-.14H/). — For  the  preparation  of  this  salt  one  part  of  tantalic 
oxide  was  fused  with  two  parts  of  cesium  carbonate.  The  melt  was 
completely  soluble  in  a small  amount  of  hot  water,  and  the  solution  on 
cooling  deposited  monoclinic  crystals  isomorphous  with  the  corresponding 
columbium  salt.  The  crystals  of  this  salt  showed  only  the  faces  of  the 
pyramids;  the  pinacoid  faces  were  not  observed.  Within  the  limits 
of  error  the  angles  were  the  same  as  those  of  the  rubidium  salt. 


OBSERVATIONS  ON  COBUMBIUM. 


1667 


Calculated:  4CS2O,  41.50;  sTajOa,  49.23;  14H2O,  9.27. 

Found:  4CS2O,  41.11;  sTagOf.,  49.16;  14H2O,  9.57. 

jCs^0.6Tafi^.s8Hfi. — A portion  of  the  above  salt  was  precipitated 
from  its  aqueous  solution  by  means  of  alcohol.  The  salt  which  separated 
gave  the  following  analysis: 

Calculated:  7CS2O,  37.01;  dTagOj,  50.17;  38H2O,  12.82. 

Found:  7CS2O,  36.97;  6Ta20s,  50.20;  38H2O,  12.81. 

Pertantalates. — Melikoff  and  Pissarjewsky  have  described  the  following 
pertantalates : 

HTaO,  + NasTaOgH 

KgTaO,  + CaKTaOs  + 4KH2O. 

Two  salts,  KgTaOg  and  NagTaOg  + 14H2O,  have  been  reported  from 
this  laboratory.^ 

The  following  additional  salts  have  been  obtained: 

RbgTaOg  MgNaTaO^.SH^O 

CSgTaOs  MgKTa0s.7H20 

MgRbTa08.9H20 
CaNaTaOg.4  KH2O 

These  salts  were  made  and  analyzed  in  the  same  manner  as  the  cor- 
responding columbium  salts.  They  were  not  as  soluble  in  water  as 
the  latter  salts. 

Rubidium  Pertantalate,  Rb^TaO^. — This  salt  was  only  prepared  in 
small  amounts  and  was  not  of  a high  degree  of  purity,  but  the  analytical 
results  obtained  are  sufficiently  accurate  to  establish  its  composition. 

Calculated:  i5Rb20,  4943l  o-5Ta205,  39.29;  4O,  11.28. 

Found:  i.sRbgO,  50.38  (diff.);  o.5Ta20s,  38.01;  4O,  11.61. 

^ Cesium  Pertantalate,  Cs^TaO^. — A sample  of  this  salt  gave  the  following 
analysis: 

Calculated:  1.5CS2O,  59-58;  o.sTagOg,  31.41;  4O,  9.01. 

Found:  1.5CS2O,  59-i8;  o.5Ta20s,  32.27;  4O,  9.09. 

Magnesium  Sodium  Pertantalate , MgNaTaO^.SH^O. — Analysis: 

Calculated:  MgO,  8.04;  o.5Na20,  6.17;  o.5Ta205,  44-39;  4O,  12.74;  8H2O,  28.66. 

Found:  MgO,  0.87;  o.sNaaO,  6.69  (diff.);  o.5Ta206,  43-98;  4O,  12.52;  8H2O,  28.74. 

Magnesium  Potassium  Pertantalate,  MgKTaO^.^H^O. — This  salt  gave 
the  following  analysis: 

Calculated:  MgO,  8.07;  0.5K2O,  9.41;  o.5Ta20s,  44-56;  4O,  12.79;  7H2O,  25.17. 

Found:  MgO,  8.06;  0.5K2O,  9.76  (diff.);  o.5Ta20s,  44.17;  4O,  12.67;  7H2O,  25.32. 

Magnesium  Rubidium  Pertantalate,  MgRbTaO^.gH^O. — Analysis: 

Calculated:  MgO,  6.93;  o.5Rb20,  16.04;  o.5Ta20s,  38.26;  4O,  10.98;  9H2O,  27.79. 

Found:  MgO,  7.10;  o.5Rb20,  15.89  (diff.);  o.5Ta20a,  38.37;  4O,  ii.oo;  9H2O,  27.64. 

^ This  Journal,  27,  1140  (1905). 


i668 


OBSl^RVATIONS  ON  COLUMBIUM. 


Calcium  Sodium  Pertantalate,  CaNaTa0s-4y2H20. — The  composition 
of  this  salt  was  perfectly  analogous  with  the  corresponding  potassium 
salt  described  by  Melikoff  and  Pissarjewsky.  It  gave  the  following 
analytical  results: 

Calculated:  CaO,  12.31;  o.sNajO,  6.81 ; o.sTagOg,  49.01;  4O,  14.07;  4.5H2O,  17.80. 

Found:  CaO,  12.81;  o.sNagO,  6.69  (diff.);  o.sTagOft,  48.85;  4O,  14.03;  4.5-H2O,  17.62. 

University  of  Pennsylvania, 

Philadelphia,  Pa. 


